diff --git a/.bumpversion.cfg b/.bumpversion.cfg
index 30af44995..ac1d31324 100644
--- a/.bumpversion.cfg
+++ b/.bumpversion.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 2.3.0
+current_version = 2.4.0.dev0
 parse = (?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)(\.(?P<release>[a-z]+)(?P<dev>\d+))?
 serialize = 
 	{major}.{minor}.{patch}.{release}{dev}
diff --git a/.mention-bot b/.mention-bot
new file mode 100644
index 000000000..f07fa548e
--- /dev/null
+++ b/.mention-bot
@@ -0,0 +1,35 @@
+{
+  "maxReviewers": 5,
+  "numFilesToCheck": 10,
+  "message": "@pullRequester, thanks! @reviewers, please review this.",
+  "alwaysNotifyForPaths": [
+    {
+      "name": "ghuser",
+      "files": ["src/js/**/*.js"],
+      "skipTeamPrs": false
+    }
+  ],
+  "fallbackNotifyForPaths": [
+    {
+      "name": "ghuser",
+      "files": ["src/js/**/*.js"],
+      "skipTeamPrs": false
+    }
+  ],
+  "findPotentialReviewers": true,
+  "fileBlacklist": ["*.md"],
+  "userBlacklist": [],
+  "userBlacklistForPR": [],
+  "requiredOrgs": [],
+  "actions": ["opened"],
+  "skipAlreadyAssignedPR": false,
+  "skipAlreadyMentionedPR": false,
+  "assignToReviewer": false,
+  "createReviewRequest": false,
+  "createComment": true,
+  "skipTitle": "",
+  "withLabel": "",
+  "delayed": false,
+  "delayedUntil": "3d",
+  "skipCollaboratorPR": false
+}
diff --git a/.travis.yml b/.travis.yml
index bf336dc9f..d059bdcde 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,17 +1,85 @@
+dist: trusty
 sudo: false
-
 language: python
-python:
-  - 2.7
-  - 3.3
-  - 3.4
-  - 3.5
-  - 3.6
-  - 3.7-dev
-
+  
 matrix:
-  allow_failures:
-    - python: 3.7-dev
+  include:
+# --------------------- XPLAT builds ------------------------
+    - python: 2.7
+      env: &xplat-env
+        - BUILD_OPTS=--xplat
+        - NUNIT_PATH=~/.nuget/packages/nunit.consolerunner/3.*/tools/nunit3-console.exe
+      addons: &xplat-addons
+        apt:
+          sources:
+          - sourceline: deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-trusty-prod trusty main
+            key_url: https://packages.microsoft.com/keys/microsoft.asc
+          - sourceline: deb http://download.mono-project.com/repo/ubuntu trusty main
+            key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xA6A19B38D3D831EF
+          packages:
+            - mono-devel
+            - ca-certificates-mono
+            - dotnet-hostfxr-2.0.0
+            - dotnet-runtime-2.0.0
+            - dotnet-sdk-2.0.0
+            
+    - python: 3.4
+      env: *xplat-env
+      addons: *xplat-addons
+
+    - python: 3.5
+      env: *xplat-env
+      addons: *xplat-addons
+
+    - python: 3.6
+      env: *xplat-env
+      addons: *xplat-addons
+      
+    - python: 3.7
+      env: *xplat-env
+      dist: xenial
+      sudo: true
+      addons: &xplat-addons-xenial
+        apt:
+          sources:
+          - sourceline: deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-xenial-prod xenial main
+            key_url: https://packages.microsoft.com/keys/microsoft.asc
+          - sourceline: deb https://download.mono-project.com/repo/ubuntu stable-xenial main
+            key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xA6A19B38D3D831EF
+          packages:
+            - mono-devel
+            - ca-certificates-mono
+            - dotnet-hostfxr-2.0.0
+            - dotnet-runtime-2.0.0
+            - dotnet-sdk-2.0.0
+
+# --------------------- Classic builds ------------------------
+    - python: 2.7
+      env: &classic-env
+        - BUILD_OPTS=
+        - NUNIT_PATH=./packages/NUnit.*/tools/nunit3-console.exe
+
+    - python: 3.4
+      env: *classic-env
+
+    - python: 3.5
+      env: *classic-env
+
+    - python: 3.6
+      env: *classic-env
+
+    - python: 3.7
+      env: *classic-env
+      dist: xenial
+      sudo: true
+      addons:
+        apt:
+          sources:
+            - sourceline: deb http://download.mono-project.com/repo/ubuntu xenial main
+              key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xA6A19B38D3D831EF
+          packages:
+            - mono-devel
+            - ca-certificates-mono
 
 env:
   global:
@@ -23,8 +91,8 @@ env:
 addons:
   apt:
     sources:
-      - mono
-      - mono-libtiff-compat
+      - sourceline: deb http://download.mono-project.com/repo/ubuntu trusty main
+        key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xA6A19B38D3D831EF
     packages:
       - mono-devel
       - ca-certificates-mono
@@ -35,12 +103,14 @@ before_install:
   - export LD_LIBRARY_PATH=$PY_LIBDIR:$LD_LIBRARY_PATH
 
 install:
+  - pip install --upgrade setuptools # TEMP - due to setuptools 36.2.0 bug
   - pip install --upgrade -r requirements.txt
-  - coverage run setup.py install
+  - coverage run setup.py install $BUILD_OPTS
 
 script:
   - python -m pytest
-  - mono ./packages/NUnit.*/tools/nunit3-console.exe src/embed_tests/bin/Python.EmbeddingTest.dll
+  - mono $NUNIT_PATH src/embed_tests/bin/Python.EmbeddingTest.dll
+  - if [[ $BUILD_OPTS == --xplat ]]; then dotnet src/embed_tests/bin/netcoreapp2.0_publish/Python.EmbeddingTest.dll; fi
 
 after_script:
   # Uncomment if need to geninterop, ie. py37 final
diff --git a/AUTHORS.md b/AUTHORS.md
index 09358586e..fe2d2b172 100644
--- a/AUTHORS.md
+++ b/AUTHORS.md
@@ -12,31 +12,50 @@
 
 ## Contributors
 
+-   Alexandre Catarino([@AlexCatarino](https://github.com/AlexCatarino))
 -   Arvid JB ([@ArvidJB](https://github.com/ArvidJB))
+-   Benoît Hudson ([@benoithudson](https://github.com/benoithudson))
 -   Bradley Friedman ([@leith-bartrich](https://github.com/leith-bartrich))
+-   Callum Noble ([@callumnoble](https://github.com/callumnoble))
 -   Christian Heimes ([@tiran](https://github.com/tiran))
 -   Christoph Gohlke ([@cgohlke](https://github.com/cgohlke))
+-   Christopher Pow ([@christopherpow](https://github.com/christopherpow))
 -   Daniel Fernandez ([@fdanny](https://github.com/fdanny))
 -   Daniel Santana ([@dgsantana](https://github.com/dgsantana))
+-   Dave Hirschfeld ([@dhirschfeld](https://github.com/dhirschfeld))
+-   David Lassonde ([@lassond](https://github.com/lassond))
 -   David Lechner ([@dlech](https://github.com/dlech))
 -   Dmitriy Se ([@dmitriyse](https://github.com/dmitriyse))
 -   He-chien Tsai ([@t3476](https://github.com/t3476))
--   Jeff Reback ([@jreback](https://github.com/jreback))
+-   Ivan Cronyn ([@cronan](https://github.com/cronan))
+-   Jan Krivanek ([@jakrivan](https://github.com/jakrivan))
+-   Jeff Reback ([@jreback](https://github.com/jreback))
 -   Joe Frayne ([@jfrayne](https://github.com/jfrayne))
 -   John Burnett ([@johnburnett](https://github.com/johnburnett))
+-   John Wilkes ([@jbw3](https://github.com/jbw3))
 -   Luke Stratman ([@lstratman](https://github.com/lstratman))
+-   Konstantin Posudevskiy ([@konstantin-posudevskiy](https://github.com/konstantin-posudevskiy))
 -   Matthias Dittrich ([@matthid](https://github.com/matthid))
 -   Patrick Stewart ([@patstew](https://github.com/patstew))
 -   Raphael Nestler ([@rnestler](https://github.com/rnestler))
+-   Rickard Holmberg ([@rickardraysearch](https://github.com/rickardraysearch))
 -   Sam Winstanley ([@swinstanley](https://github.com/swinstanley))
 -   Sean Freitag ([@cowboygneox](https://github.com/cowboygneox))
 -   Serge Weinstock ([@sweinst](https://github.com/sweinst))
+-   Simon Mourier ([@smourier](https://github.com/smourier))
+-   Viktoria Kovescses ([@vkovec](https://github.com/vkovec))
+-   Ville M. Vainio ([@vivainio](https://github.com/vivainio))
 -   Virgil Dupras ([@hsoft](https://github.com/hsoft))
 -   Wenguang Yang ([@yagweb](https://github.com/yagweb))
+-   William Sardar ([@williamsardar])(https://github.com/williamsardar)
 -   Xavier Dupré ([@sdpython](https://github.com/sdpython))
 -   Zane Purvis ([@zanedp](https://github.com/zanedp))
 -   ([@bltribble](https://github.com/bltribble))
+-   ([@civilx64](https://github.com/civilx64))
+-   ([@GSPP](https://github.com/GSPP))
 -   ([@omnicognate](https://github.com/omnicognate))
 -   ([@rico-chet](https://github.com/rico-chet))
 -   ([@rmadsen-ks](https://github.com/rmadsen-ks))
 -   ([@stonebig](https://github.com/stonebig))
+-   ([@testrunner123](https://github.com/testrunner123))
+
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c7de23c7..a3816cd0c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,74 +5,122 @@ This project adheres to [Semantic Versioning][].
 
 This document follows the conventions laid out in [Keep a CHANGELOG][].
 
+## [unreleased][]
+
+### Added
+
+-   Added support for embedding python into dotnet core 2.0 (NetStandard 2.0)
+-   Added new build system (pythonnet.15.sln) based on dotnetcore-sdk/xplat(crossplatform msbuild).
+    Currently there two side-by-side build systems that produces the same output (net40) from the same sources.
+    After a some transition time, current (mono/ msbuild 14.0) build system will be removed.
+-   NUnit upgraded to 3.7 (eliminates travis-ci random bug)
+-   Added C# `PythonEngine.AddShutdownHandler` to help client code clean up on shutdown.
+-   Added `clr.GetClrType` ([#432][i432])([#433][p433])
+-   Allowed passing `None` for nullable args ([#460][p460])
+-   Added keyword arguments based on C# syntax for calling CPython methods ([#461][p461])
+-   Catches exceptions thrown in C# iterators (yield returns) and rethrows them in python ([#475][i475])([#693][p693])
+-   Implemented GetDynamicMemberNames() for PyObject to allow dynamic object members to be visible in the debugger ([#443][i443])([#690][p690])
+-   Incorporated reference-style links to issues and pull requests in the CHANGELOG ([#608][i608])
+-   Added detailed comments about aproaches and dangers to handle multi-app-domains ([#625][p625])
+-   Python 3.7 support, builds and testing added. Defaults changed from Python 3.6 to 3.7 ([#698][p698])
+
+### Changed
+
+-   Reattach python exception traceback information (#545)
+-   PythonEngine.Intialize will now call `Py_InitializeEx` with a default value of 0, so signals will not be configured by default on embedding. This is different from the previous behaviour, where `Py_Initialize` was called instead, which sets initSigs to 1. ([#449][i449])
+
+### Fixed
+
+-   Fixed secondary PythonEngine.Initialize call, all sensitive static variables now reseted.
+    This is a hidden bug. Once python cleaning up enough memory, objects from previous engine run becomes corrupted. ([#534][p534])
+-   Fixed Visual Studio 2017 compat ([#434][i434]) for setup.py
+-   Fixed crashes when integrating pythonnet in Unity3d ([#714][i714]),
+    related to unloading the Application Domain
+-   Fixed interop methods with Py_ssize_t. NetCoreApp 2.0 is more sensitive than net40 and requires this fix. ([#531][p531])
+-   Fixed crash on exit of the Python interpreter if a python class
+    derived from a .NET class has a `__namespace__` or `__assembly__`
+    attribute ([#481][i481])
+-   Fixed conversion of 'float' and 'double' values ([#486][i486])
+-   Fixed 'clrmethod' for python 2 ([#492][i492])
+-   Fixed double calling of constructor when deriving from .NET class ([#495][i495])
+-   Fixed `clr.GetClrType` when iterating over `System` members ([#607][p607]) 
+-   Fixed `LockRecursionException` when loading assemblies ([#627][i627])
+-   Fixed errors breaking .NET Remoting on method invoke ([#276][i276])
+-   Fixed PyObject.GetHashCode ([#676][i676])
+-   Fix memory leaks due to spurious handle incrementation ([#691][i691])
+-   Fix spurious assembly loading exceptions from private types ([#703][i703])
+-   Fix inheritance of non-abstract base methods ([#755][i755])
+
+
 ## [2.3.0][] - 2017-03-11
 
 ### Added
 
--   Added Code Coverage (#345)
--   Added `PySys_SetArgvEx` (#347)
--   Added XML Documentation (#349)
--   Added `Embedded_Tests` on AppVeyor (#224)(#353)
--   Added `Embedded_Tests` on Travis (#224)(#391)
--   Added PY3 settings to solution configuration-manager (#346)
--   Added `Slack` (#384)(#383)(#386)
+-   Added Code Coverage ([#345][p345])
+-   Added `PySys_SetArgvEx` ([#347][p347])
+-   Added XML Documentation ([#349][p349])
+-   Added `Embedded_Tests` on AppVeyor ([#224][i224])([#353][p353])
+-   Added `Embedded_Tests` on Travis ([#224][i224])([#391][p391])
+-   Added PY3 settings to solution configuration-manager ([#346][p346])
+-   Added `Slack` ([#384][p384])([#383][i383])([#386][p386])
 -   Added function of passing an arbitrary .NET object as the value
-    of an attribute of `PyObject` (#370)(#373)
--   Added `Coverity scan` (#390)
--   Added `bumpversion` for version control (#319)(#398)
--   Added `tox` for local testing (#345)
+    of an attribute of `PyObject` ([#370][i370])([#373][p373])
+-   Added `Coverity scan` ([#390][i390])
+-   Added `bumpversion` for version control ([#319][i319])([#398][p398])
+-   Added `tox` for local testing ([#345][p345])
 -   Added `requirements.txt`
--   Added to `PythonEngine` methods `Eval` and `Exec` (#389)
--   Added implementations of `ICustomMarshal` (#407)
--   Added docker images (#322)
--   Added hooks in `pyinstaller` and `cx_freeze` for `pythonnet` (#66)
+-   Added to `PythonEngine` methods `Eval` and `Exec` ([#389][p389])
+-   Added implementations of `ICustomMarshal` ([#407][p407])
+-   Added docker images ([#322][i322])
+-   Added hooks in `pyinstaller` and `cx_freeze` for `pythonnet` ([#66][i66])
 
 ### Changed
 
--   Refactored python `unittests` (#329)
--   Refactored python `setup.py` (#337)
--   Refactored remaining of Build Directives on `runtime.cs` (#339)
--   Refactored `Embedded_Tests` to make easier to write tests (#369)
--   Changed `unittests` to `pytest` (#368)
--   Upgraded NUnit framework from `2.6.3` to `3.5.0` (#341)
--   Downgraded NUnit framework from `3.5.0` to `2.6.4` (#353)
--   Upgraded NUnit framework from `2.6.4` to `3.6.0` (#371)
--   Unfroze Mono version on Travis (#345)
--   Changed `conda.recipe` build to only pull-requests (#345)
--   Combine `Py_DEBUG` and `PYTHON_WITH_PYDEBUG` flags (#362)
+-   Refactored python `unittests` ([#329][p329])
+-   Refactored python `setup.py` ([#337][p337])
+-   Refactored remaining of Build Directives on `runtime.cs` ([#339][p339])
+-   Refactored `Embedded_Tests` to make easier to write tests ([#369][p369])
+-   Changed `unittests` to `pytest` ([#368][p368])
+-   Upgraded NUnit framework from `2.6.3` to `3.5.0` ([#341][p341])
+-   Downgraded NUnit framework from `3.5.0` to `2.6.4` ([#353][p353])
+-   Upgraded NUnit framework from `2.6.4` to `3.6.0` ([#371][p371])
+-   Unfroze Mono version on Travis ([#345][p345])
+-   Changed `conda.recipe` build to only pull-requests ([#345][p345])
+-   Combine `Py_DEBUG` and `PYTHON_WITH_PYDEBUG` flags ([#362][i362])
 
 ### Deprecated
 
--   Deprecated `RunString` (#401)
+-   Deprecated `RunString` ([#401][i401])
 
 ### Fixed
 
--   Fixed crash during Initialization (#262)(#343)
--   Fixed crash during Shutdown (#365)
+-   Fixed crash during Initialization ([#262][i262])([#343][p343])
+-   Fixed crash during Shutdown ([#365][p365])
 -   Fixed multiple build warnings
--   Fixed method signature match for Object Type (#203)(#377)
--   Fixed outdated version number in AssemblyInfo (#398)
--   Fixed wrong version number in `conda.recipe` (#398)
+-   Fixed method signature match for Object Type ([#203][i203])([#377][p377])
+-   Fixed outdated version number in AssemblyInfo ([#398][p398])
+-   Fixed wrong version number in `conda.recipe` ([#398][p398])
 -   Fixed fixture location for Python tests and `Embedded_Tests`
--   Fixed `PythonException` crash during Shutdown (#400)
--   Fixed `AppDomain` unload during GC (#397)(#400)
--   Fixed `Py_Main` & `PySys_SetArgvEx` `no mem error` on `UCS4/PY3` (#399)
--   Fixed `Python.Runtime.dll.config` on macOS (#120)
--   Fixed crash on `PythonEngine.Version` (#413)
--   Fixed `PythonEngine.PythonPath` issues (#179)(#414)(#415)
+-   Fixed `PythonException` crash during Shutdown ([#400][p400])
+-   Fixed `AppDomain` unload during GC ([#397][i397])([#400][p400])
+-   Fixed `Py_Main` & `PySys_SetArgvEx` `no mem error` on `UCS4/PY3` ([#399][p399])
+-   Fixed `Python.Runtime.dll.config` on macOS ([#120][i120])
+-   Fixed crash on `PythonEngine.Version` ([#413][i413])
+-   Fixed `PythonEngine.PythonPath` issues ([#179][i179])([#414][i414])([#415][p415])
+-   Fixed missing information on 'No method matches given arguments' by adding the method name
 
 ### Removed
 
--   Removed `six` dependency for `unittests` (#329)
--   Removed `Mono.Unix` dependency for `UCS4` (#360)
+-   Removed `six` dependency for `unittests` ([#329][p329])
+-   Removed `Mono.Unix` dependency for `UCS4` ([#360][p360])
 -   Removed need for `Python.Runtime.dll.config`
--   Removed PY32 build option `PYTHON_WITH_WIDE_UNICODE` (#417)
+-   Removed PY32 build option `PYTHON_WITH_WIDE_UNICODE` ([#417][i417])
 
 ## [2.2.2][] - 2017-01-29
 
 ### Fixed
 
--   Missing files from packaging (#336)
+-   Missing files from packaging ([#336][i336])
 
 ## [2.2.1][] - 2017-01-26
 
@@ -80,65 +128,65 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 
 ### Added
 
--   Python 3.6 support (#310)
--   Added `__version__` to module (#312)
--   Added `conda` recipe (#281)
--   Nuget update on build (#268)
--   Added `__cause__` attribute on exception (#287)
+-   Python 3.6 support ([#310][p310])
+-   Added `__version__` to module ([#312][p312])
+-   Added `conda` recipe ([#281][p281])
+-   Nuget update on build ([#268][p268])
+-   Added `__cause__` attribute on exception ([#287][p287])
 
 ### Changed
 
--   License to MIT (#314)
--   Project clean-up (#320)
+-   License to MIT ([#314][p314])
+-   Project clean-up ([#320][p320])
 -   Refactor `#if` directives
--   Rename Decref/Incref to XDecref/XIncre (#275)
--   Remove printing if Decref is called with NULL (#275)
+-   Rename Decref/Incref to XDecref/XIncre ([#275][p275])
+-   Remove printing if Decref is called with NULL ([#275][p275])
 
 ### Removed
 
--   Python 2.6 support (#270)
--   Python 3.2 support (#270)
+-   Python 2.6 support ([#270][i270])
+-   Python 3.2 support ([#270][i270])
 
 ### Fixed
 
--   Fixed `isinstance` refcount_leak (#273)
--   Comparison Operators (#294)
--   Improved Linux support (#300)
--   Exception pickling (#286)
+-   Fixed `isinstance` refcount_leak ([#273][p273])
+-   Comparison Operators ([#294][p294])
+-   Improved Linux support ([#300][p300])
+-   Exception pickling ([#286][p286])
 
 ## [2.2.0-dev1][] - 2016-09-19
 
 ### Changed
 
--   Switch to C# 6.0 (#219)
--   `setup.py` improvements for locating build tools (#208)
--   unmanaged exports updated (#206)
--   Mono update pinned to 4.2.4.4 (#233)
+-   Switch to C# 6.0 ([#219][p219])
+-   `setup.py` improvements for locating build tools ([#208][p208])
+-   unmanaged exports updated ([#206][p206])
+-   Mono update pinned to 4.2.4.4 ([#233][p233])
 
 ### Fixed
 
--   Fixed relative imports (#219)
--   Fixed recursive types (#250)
--   Demo fix - stream reading (#225)
+-   Fixed relative imports ([#219][p219])
+-   Fixed recursive types ([#250][p250])
+-   Demo fix - stream reading ([#225][p225])
 
 ## [2.1.0][] - 2016-04-12
 
 ### Added
 
--   Added Python 3.2 support. (#78)
--   Added Python 3.3 support. (#78)
--   Added Python 3.4 support. (#78)
--   Added Python 3.5 support. (#163)
--   Managed types can be sub-classed in Python (#78)
--   Uses dynamic objects for cleaner code when embedding Python (#78)
+-   Added Python 3.2 support. ([#78][p78])
+-   Added Python 3.3 support. ([#78][p78])
+-   Added Python 3.4 support. ([#78][p78])
+-   Added Python 3.5 support. ([#163][p163])
+-   Managed types can be sub-classed in Python ([#78][p78])
+-   Uses dynamic objects for cleaner code when embedding Python ([#78][p78])
 
 ### Changed
 
--   Better Linux support (with or without --enable-shared option) (#78)
+-   Better Linux support (with or without --enable-shared option) ([#78][p78])
 
 ### Removed
 
--   Implicit Type Casting (#131)
+-   Implicit Type Casting ([#131][i131])
 
 ## [2.0.0][] - 2015-06-26
 
@@ -558,3 +606,101 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 [2.0.0]: ../../compare/1.0...v2.0.0
 
 [1.0.0]: https://github.com/pythonnet/pythonnet/releases/tag/1.0
+
+[i714]: https://github.com/pythonnet/pythonnet/issues/714
+[i608]: https://github.com/pythonnet/pythonnet/issues/608
+[i443]: https://github.com/pythonnet/pythonnet/issues/443
+[p690]: https://github.com/pythonnet/pythonnet/pull/690
+[i475]: https://github.com/pythonnet/pythonnet/issues/475
+[p693]: https://github.com/pythonnet/pythonnet/pull/693
+[i432]: https://github.com/pythonnet/pythonnet/issues/432
+[p433]: https://github.com/pythonnet/pythonnet/pull/433
+[p460]: https://github.com/pythonnet/pythonnet/pull/460
+[p461]: https://github.com/pythonnet/pythonnet/pull/461
+[p433]: https://github.com/pythonnet/pythonnet/pull/433
+[i434]: https://github.com/pythonnet/pythonnet/issues/434
+[i481]: https://github.com/pythonnet/pythonnet/issues/481
+[i486]: https://github.com/pythonnet/pythonnet/issues/486
+[i492]: https://github.com/pythonnet/pythonnet/issues/492
+[i495]: https://github.com/pythonnet/pythonnet/issues/495
+[p607]: https://github.com/pythonnet/pythonnet/pull/607
+[i627]: https://github.com/pythonnet/pythonnet/issues/627
+[i276]: https://github.com/pythonnet/pythonnet/issues/276
+[i676]: https://github.com/pythonnet/pythonnet/issues/676
+[p345]: https://github.com/pythonnet/pythonnet/pull/345
+[p347]: https://github.com/pythonnet/pythonnet/pull/347
+[p349]: https://github.com/pythonnet/pythonnet/pull/349
+[i224]: https://github.com/pythonnet/pythonnet/issues/224
+[p353]: https://github.com/pythonnet/pythonnet/pull/353
+[p391]: https://github.com/pythonnet/pythonnet/pull/391
+[p346]: https://github.com/pythonnet/pythonnet/pull/346
+[p384]: https://github.com/pythonnet/pythonnet/pull/384
+[i383]: https://github.com/pythonnet/pythonnet/issues/383
+[p386]: https://github.com/pythonnet/pythonnet/pull/386
+[i370]: https://github.com/pythonnet/pythonnet/issues/370
+[p373]: https://github.com/pythonnet/pythonnet/pull/373
+[i390]: https://github.com/pythonnet/pythonnet/issues/390
+[i319]: https://github.com/pythonnet/pythonnet/issues/319
+[p398]: https://github.com/pythonnet/pythonnet/pull/398
+[p345]: https://github.com/pythonnet/pythonnet/pull/345
+[p389]: https://github.com/pythonnet/pythonnet/pull/389
+[p407]: https://github.com/pythonnet/pythonnet/pull/407
+[i322]: https://github.com/pythonnet/pythonnet/issues/322
+[i66]: https://github.com/pythonnet/pythonnet/issues/66
+[p329]: https://github.com/pythonnet/pythonnet/pull/329
+[p337]: https://github.com/pythonnet/pythonnet/pull/337
+[p339]: https://github.com/pythonnet/pythonnet/pull/339
+[p369]: https://github.com/pythonnet/pythonnet/pull/369
+[p368]: https://github.com/pythonnet/pythonnet/pull/368
+[p341]: https://github.com/pythonnet/pythonnet/pull/341
+[p353]: https://github.com/pythonnet/pythonnet/pull/353
+[p371]: https://github.com/pythonnet/pythonnet/pull/371
+[p345]: https://github.com/pythonnet/pythonnet/pull/345
+[i362]: https://github.com/pythonnet/pythonnet/issues/362
+[i401]: https://github.com/pythonnet/pythonnet/issues/401
+[i262]: https://github.com/pythonnet/pythonnet/issues/262
+[p343]: https://github.com/pythonnet/pythonnet/pull/343
+[p365]: https://github.com/pythonnet/pythonnet/pull/365
+[i203]: https://github.com/pythonnet/pythonnet/issues/203
+[p377]: https://github.com/pythonnet/pythonnet/pull/377
+[p398]: https://github.com/pythonnet/pythonnet/pull/398
+[p400]: https://github.com/pythonnet/pythonnet/pull/400
+[i397]: https://github.com/pythonnet/pythonnet/issues/397
+[p399]: https://github.com/pythonnet/pythonnet/pull/399
+[i120]: https://github.com/pythonnet/pythonnet/issues/120
+[i413]: https://github.com/pythonnet/pythonnet/issues/413
+[i179]: https://github.com/pythonnet/pythonnet/issues/179
+[i414]: https://github.com/pythonnet/pythonnet/issues/414
+[p415]: https://github.com/pythonnet/pythonnet/pull/415
+[p329]: https://github.com/pythonnet/pythonnet/pull/329
+[p360]: https://github.com/pythonnet/pythonnet/pull/360
+[i417]: https://github.com/pythonnet/pythonnet/issues/417
+[i336]: https://github.com/pythonnet/pythonnet/issues/336
+[p310]: https://github.com/pythonnet/pythonnet/pull/310
+[p312]: https://github.com/pythonnet/pythonnet/pull/312
+[p281]: https://github.com/pythonnet/pythonnet/pull/281
+[p268]: https://github.com/pythonnet/pythonnet/pull/268
+[p287]: https://github.com/pythonnet/pythonnet/pull/287
+[p314]: https://github.com/pythonnet/pythonnet/pull/314
+[p320]: https://github.com/pythonnet/pythonnet/pull/320
+[p275]: https://github.com/pythonnet/pythonnet/pull/275
+[i270]: https://github.com/pythonnet/pythonnet/issues/270
+[p273]: https://github.com/pythonnet/pythonnet/pull/273
+[p294]: https://github.com/pythonnet/pythonnet/pull/294
+[p300]: https://github.com/pythonnet/pythonnet/pull/300
+[p286]: https://github.com/pythonnet/pythonnet/pull/286
+[p219]: https://github.com/pythonnet/pythonnet/pull/219
+[p208]: https://github.com/pythonnet/pythonnet/pull/208
+[p206]: https://github.com/pythonnet/pythonnet/pull/206
+[p233]: https://github.com/pythonnet/pythonnet/pull/233
+[p219]: https://github.com/pythonnet/pythonnet/pull/219
+[p250]: https://github.com/pythonnet/pythonnet/pull/250
+[p225]: https://github.com/pythonnet/pythonnet/pull/225
+[p78]: https://github.com/pythonnet/pythonnet/pull/78
+[p163]: https://github.com/pythonnet/pythonnet/pull/163
+[p625]: https://github.com/pythonnet/pythonnet/pull/625
+[i131]: https://github.com/pythonnet/pythonnet/issues/131
+[p531]: https://github.com/pythonnet/pythonnet/pull/531
+[i755]: https://github.com/pythonnet/pythonnet/pull/755
+[p534]: https://github.com/pythonnet/pythonnet/pull/534
+[i449]: https://github.com/pythonnet/pythonnet/issues/449
diff --git a/NuGet.config b/NuGet.config
new file mode 100644
index 000000000..5210cd6c9
--- /dev/null
+++ b/NuGet.config
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <add key="dot-net MyGet Feed" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" protocolVersion="3"/>
+    <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
+  </packageSources>
+</configuration>
\ No newline at end of file
diff --git a/README.md b/README.md
index 2794298a6..7e859481d 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 # pythonnet - Python for .NET
 
+[![Join the chat at https://gitter.im/pythonnet/pythonnet](https://badges.gitter.im/pythonnet/pythonnet.svg)](https://gitter.im/pythonnet/pythonnet?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
 [![appveyor shield][]](https://ci.appveyor.com/project/pythonnet/pythonnet/branch/master)
 [![travis shield][]](https://travis-ci.org/pythonnet/pythonnet)
 [![codecov shield][]](https://codecov.io/github/pythonnet/pythonnet)
@@ -42,7 +44,7 @@ from System.Windows.Forms import Form
     a `using (Py.GIL()) {/* Your code here */}` block.
 -   Import python modules using `dynamic mod = Py.Import("mod")`,
     then you can call functions as normal, eg `mod.func(args)`.
--   Use `mod.func(args, Py.kw("keywordargname", keywordargvalue))`
+-   Use `mod.func(args, Py.kw("keywordargname", keywordargvalue))` or `mod.func(args, keywordargname: keywordargvalue)`
     to apply keyword arguments.
 -   All python objects should be declared as `dynamic` type.
 -   Mathematical operations involving python and literal/managed types must
@@ -63,15 +65,14 @@ static void Main(string[] args)
 
         double c = np.cos(5) + sin(5);
         Console.WriteLine(c);
-        /* this block is temporarily disabled due to regression #249
+
         dynamic a = np.array(new List<float> { 1, 2, 3 });
         Console.WriteLine(a.dtype);
 
-        dynamic b = np.array(new List<float> { 6, 5, 4 }, Py.kw("dtype", np.int32));
+        dynamic b = np.array(new List<float> { 6, 5, 4 }, dtype: np.int32);
         Console.WriteLine(b.dtype);
 
         Console.WriteLine(a * b);
-        */
         Console.ReadKey();
     }
 }
@@ -88,6 +89,10 @@ int32
 [  6.  10.  12.]
 ```
 
+Information on installation, FAQ, troubleshooting, debugging, and projects using pythonnet can be found in the Wiki:
+
+https://github.com/pythonnet/pythonnet/wiki
+
 [appveyor shield]: https://img.shields.io/appveyor/ci/pythonnet/pythonnet/master.svg?label=AppVeyor
 
 [codecov shield]: https://img.shields.io/codecov/c/github/pythonnet/pythonnet/master.svg?label=Codecov
diff --git a/appveyor.yml b/appveyor.yml
index c108801e7..ce345cbf8 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,6 +1,9 @@
 version: '{branch}-{build}'
 build: off
 
+image:
+  - Visual Studio 2017
+  
 platform:
   - x86
   - x64
@@ -12,11 +15,27 @@ environment:
     CODECOV_ENV: PYTHON_VERSION, PLATFORM
 
   matrix:
+    - PYTHON_VERSION: 2.7 
+      BUILD_OPTS: --xplat
+    - PYTHON_VERSION: 3.4
+      BUILD_OPTS: --xplat
+    - PYTHON_VERSION: 3.5
+      BUILD_OPTS: --xplat
+    - PYTHON_VERSION: 3.6
+      BUILD_OPTS: --xplat
+    - PYTHON_VERSION: 3.7
+      BUILD_OPTS: --xplat
     - PYTHON_VERSION: 2.7
-    - PYTHON_VERSION: 3.3
     - PYTHON_VERSION: 3.4
     - PYTHON_VERSION: 3.5
     - PYTHON_VERSION: 3.6
+    - PYTHON_VERSION: 3.7
+
+matrix:
+    allow_failures:
+      - PYTHON_VERSION: 3.4
+        BUILD_OPTS: --xplat
+      - PYTHON_VERSION: 3.4
 
 init:
   # Update Environment Variables based on matrix/platform
@@ -28,6 +47,7 @@ init:
   - set PATH=%PYTHON%;%PYTHON%\Scripts;%PATH%
 
 install:
+  - python -m pip install -U pip
   - pip install --upgrade -r requirements.txt --quiet
 
   # Install OpenCover. Can't put on `packages.config`, not Mono compatible
@@ -37,7 +57,7 @@ build_script:
   # Create clean `sdist`. Only used for releases
   - python setup.py --quiet sdist
   # Build `wheel` with coverage of `setup.py`
-  - coverage run setup.py bdist_wheel
+  - coverage run setup.py bdist_wheel %BUILD_OPTS%
 
 test_script:
   - pip install --no-index --find-links=.\dist\ pythonnet
@@ -47,11 +67,11 @@ test_script:
 on_finish:
   # Temporary disable multiple upload due to codecov limit of 20 per commit.
   # https://docs.codecov.io/blog/week-8-2017
-  # - coverage xml -i
+  - coverage xml -i
   # - codecov --file coverage.xml --flags setup_windows
   # - codecov --file py.coverage --flags python_tests
   # - codecov --file cs.coverage --flags embedded_tests
-  - codecov --flags setup_windows
+  - codecov --file py.coverage cs.coverage coverage.xml --flags setup_windows
 
 artifacts:
   - path: dist\*
diff --git a/ci/appveyor_build_recipe.ps1 b/ci/appveyor_build_recipe.ps1
index 52520f4c2..84e0bc7c6 100644
--- a/ci/appveyor_build_recipe.ps1
+++ b/ci/appveyor_build_recipe.ps1
@@ -11,7 +11,7 @@ if ($env:PLATFORM -eq "x86"){
     $env:CONDA_BLD = "$env:CONDA_BLD" + "-x64"
 }
 
-if ($env:APPVEYOR_PULL_REQUEST_NUMBER -or $env:FORCE_CONDA_BUILD -eq "True") {
+if ($env:APPVEYOR_PULL_REQUEST_NUMBER -or $env:APPVEYOR_REPO_TAG_NAME -or $env:FORCE_CONDA_BUILD -eq "True") {
     # Update PATH, and keep a copy to restore at end of this PowerShell script
     $old_path = $env:path
     $env:path = "$env:CONDA_BLD;$env:CONDA_BLD\Scripts;" + $env:path
diff --git a/ci/appveyor_run_tests.ps1 b/ci/appveyor_run_tests.ps1
index 4245d1577..b45440fbe 100644
--- a/ci/appveyor_run_tests.ps1
+++ b/ci/appveyor_run_tests.ps1
@@ -11,7 +11,12 @@ if ($FALSE -and $env:PLATFORM -eq "x86"){
 # Executable paths for OpenCover
 # Note if OpenCover fails, it won't affect the exit codes.
 $OPENCOVER = Resolve-Path .\packages\OpenCover.*\tools\OpenCover.Console.exe
-$CS_RUNNER = Resolve-Path .\packages\NUnit.*\tools\"$CS_RUNNER".exe
+if ($env:BUILD_OPTS -eq "--xplat"){
+    $CS_RUNNER = Resolve-Path $env:USERPROFILE\.nuget\packages\nunit.consolerunner\*\tools\"$CS_RUNNER".exe
+}
+else{
+    $CS_RUNNER = Resolve-Path .\packages\NUnit.*\tools\"$CS_RUNNER".exe
+}
 $PY = Get-Command python
 
 # Can't use ".\build\*\Python.EmbeddingTest.dll". Missing framework files.
@@ -39,6 +44,23 @@ if ($CS_STATUS -ne 0) {
     Write-Host "Embedded tests failed" -ForegroundColor "Red"
 }
 
+if ($env:BUILD_OPTS -eq "--xplat"){
+    if ($env:PLATFORM -eq "x64") {
+         $DOTNET_CMD = "dotnet"
+    }
+    else{
+         $DOTNET_CMD = "c:\Program Files (x86)\dotnet\dotnet"
+    }
+
+    # Run Embedded tests for netcoreapp2.0 (OpenCover currently does not supports dotnet core)
+    Write-Host ("Starting embedded tests for netcoreapp2.0") -ForegroundColor "Green"
+    &$DOTNET_CMD .\src\embed_tests\bin\netcoreapp2.0_publish\Python.EmbeddingTest.dll
+    $CS_STATUS = $LastExitCode
+    if ($CS_STATUS -ne 0) {
+        Write-Host "Embedded tests for netcoreapp2.0 failed" -ForegroundColor "Red"
+    }
+}
+
 # Set exit code to fail if either Python or Embedded tests failed
 if ($PYTHON_STATUS -ne 0 -or $CS_STATUS -ne 0) {
     Write-Host "Tests failed" -ForegroundColor "Red"
diff --git a/conda.recipe/bld.bat b/conda.recipe/bld.bat
index 1495f877d..27b55f2de 100644
--- a/conda.recipe/bld.bat
+++ b/conda.recipe/bld.bat
@@ -1,6 +1,6 @@
 :: build it
 
 :: set path to modern MSBuild
-set PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;%PATH%
+set PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;C:\Program Files (x86)\MSBuild\15.0\Bin;%PATH%
 
 %PYTHON% setup.py install
diff --git a/conda.recipe/meta.yaml b/conda.recipe/meta.yaml
index 98602481f..3641185bb 100644
--- a/conda.recipe/meta.yaml
+++ b/conda.recipe/meta.yaml
@@ -1,6 +1,6 @@
 package:
   name: pythonnet
-  version: "2.3.0"
+  version: "2.4.0.dev0"
 
 build:
   skip: True  # [not win]
diff --git a/demo/DynamicGrid.py b/demo/DynamicGrid.py
new file mode 100644
index 000000000..951a6c248
--- /dev/null
+++ b/demo/DynamicGrid.py
@@ -0,0 +1,23 @@
+import clr
+import sys
+if sys.platform.lower() not in ['cli','win32']:
+    print("only windows is supported for wpf")
+clr.AddReference(r"wpf\PresentationFramework")
+from System.IO import StreamReader
+from System.Windows.Markup import XamlReader
+from System.Threading import Thread, ThreadStart, ApartmentState
+from System.Windows import Application, Window
+
+
+class MyWindow(Window):
+    def __init__(self):
+        stream = StreamReader("DynamicGrid.xaml")
+        window = XamlReader.Load(stream.BaseStream)
+        Application().Run(window)
+            
+
+if __name__ == '__main__':
+    thread = Thread(ThreadStart(MyWindow))
+    thread.SetApartmentState(ApartmentState.STA)
+    thread.Start()
+    thread.Join()
diff --git a/demo/DynamicGrid.xaml b/demo/DynamicGrid.xaml
new file mode 100644
index 000000000..3c82eb16d
--- /dev/null
+++ b/demo/DynamicGrid.xaml
@@ -0,0 +1,34 @@
+<Window 
+       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
+       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
+       Title="WpfApplication1" Height="300" Width="300">
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="*"/>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="*"/>
+        </Grid.RowDefinitions>
+        <Grid.ColumnDefinitions>
+            <ColumnDefinition Width="*"/>
+            <ColumnDefinition Width="Auto"/>
+            <ColumnDefinition Width="*"/>
+        </Grid.ColumnDefinitions>
+        <Label Content="Left" Grid.Column="0" Background="LightBlue" />
+        <GridSplitter 
+                    VerticalAlignment="Stretch" 
+                    HorizontalAlignment="Stretch"
+                    Grid.Column="1"
+                    Width="5" 
+                    Grid.RowSpan="3"/>
+        <Label Content="Right" Grid.Column="2" Grid.Row="2" Background="LightBlue" />
+        <Label Content="Top" Grid.Column="2" Background="LightGreen"/>
+        <GridSplitter 
+                    HorizontalAlignment="Stretch"
+                    VerticalAlignment="Stretch"
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index 000000000..f2015e480
--- /dev/null
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+		{F94B547A-E97E-4500-8D53-B4D64D076E5F}.ReleaseWin|x86.Build.0 = ReleaseWin|x86
+		{F94B547A-E97E-4500-8D53-B4D64D076E5F}.ReleaseWinPY3|x64.ActiveCfg = ReleaseWinPY3|x64
+		{F94B547A-E97E-4500-8D53-B4D64D076E5F}.ReleaseWinPY3|x64.Build.0 = ReleaseWinPY3|x64
+		{F94B547A-E97E-4500-8D53-B4D64D076E5F}.ReleaseWinPY3|x86.ActiveCfg = ReleaseWinPY3|x86
+		{F94B547A-E97E-4500-8D53-B4D64D076E5F}.ReleaseWinPY3|x86.Build.0 = ReleaseWinPY3|x86
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {A6347B90-BBE6-4E45-90BF-1BD8B76069E3}
+	EndGlobalSection
+EndGlobal
diff --git a/requirements.txt b/requirements.txt
index bcceedf25..29c2e4566 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,12 +1,12 @@
 # Requirements for both Travis and AppVeyor
-pytest
+pytest==3.2.5
 coverage
+psutil
+
+# Coverage upload
+codecov
 
 # Platform specific requirements
-pip; sys_platform == 'win32'
+# pip; sys_platform == 'win32'
 wheel; sys_platform == 'win32'
 pycparser; sys_platform != 'win32'
-
-# Coverage upload
-# codecov v2.0.6 isn't on PyPi
-https://github.com/codecov/codecov-python/tarball/v2.0.6
diff --git a/setup.py b/setup.py
index b85e2c8ad..1b6f07ea6 100644
--- a/setup.py
+++ b/setup.py
@@ -14,14 +14,15 @@
 import sys
 import sysconfig
 from distutils import spawn
-from distutils.command import build_ext, install_data, install_lib
+from distutils.command import install, build, build_ext, install_data, install_lib
+from wheel import bdist_wheel
 
 from setuptools import Extension, setup
 
 # Allow config/verbosity to be set from cli
 # http://stackoverflow.com/a/4792601/5208670
 CONFIG = "Release"  # Release or Debug
-VERBOSITY = "minimal"  # quiet, minimal, normal, detailed, diagnostic
+VERBOSITY = "normal"  # quiet, minimal, normal, detailed, diagnostic
 
 is_64bits = sys.maxsize > 2**32
 DEVTOOLS = "MsDev" if sys.platform == "win32" else "Mono"
@@ -39,6 +40,12 @@
 kits_suffix = os.path.join("bin", ARCH)
 
 WIN_SDK_KEYS = (
+    RegKey(sdk_name="Windows Kit 10.0", key=kits_root,
+           value_name="KitsRoot10", suffix=os.path.join("bin", "10.0.16299.0", ARCH)),
+
+    RegKey(sdk_name="Windows Kit 10.0", key=kits_root,
+           value_name="KitsRoot10", suffix=os.path.join("bin", "10.0.15063.0", ARCH)),
+
     RegKey(sdk_name="Windows Kit 10.0", key=kits_root,
            value_name="KitsRoot10", suffix=kits_suffix),
 
@@ -65,6 +72,9 @@
 )
 
 VS_KEYS = (
+    RegKey(sdk_name="MSBuild 15", key=vs_root.format("15.0"),
+           value_name="MSBuildToolsPath", suffix=""),
+
     RegKey(sdk_name="MSBuild 14", key=vs_root.format("14.0"),
            value_name="MSBuildToolsPath", suffix=""),
 
@@ -128,9 +138,28 @@ def _get_long_description():
     except ImportError:
         return '.Net and Mono integration for Python'
 
+def _update_xlat_devtools():
+    global DEVTOOLS
+    if DEVTOOLS == "MsDev":
+        DEVTOOLS = "MsDev15"
+    elif DEVTOOLS == "Mono":
+        DEVTOOLS = "dotnet"
 
 class BuildExtPythonnet(build_ext.build_ext):
+    user_options = build_ext.build_ext.user_options + [
+            ('xplat', None, None)
+        ]
+    def initialize_options(self):
+        build_ext.build_ext.initialize_options(self)
+        self.xplat = None
+
+    def finalize_options(self):
+        build_ext.build_ext.finalize_options(self)
+
     def build_extension(self, ext):
+        if self.xplat:
+             _update_xlat_devtools()
+
         """Builds the .pyd file using msbuild or xbuild"""
         if ext.name != "clr":
             return build_ext.build_ext.build_extension(self, ext)
@@ -161,7 +190,7 @@ def build_extension(self, ext):
         if CONFIG == "Debug":
             defines.extend(["DEBUG", "TRACE"])
 
-        if sys.platform != "win32" and DEVTOOLS == "Mono":
+        if sys.platform != "win32" and (DEVTOOLS == "Mono" or DEVTOOLS == "dotnet"):
             on_darwin = sys.platform == "darwin"
             defines.append("MONO_OSX" if on_darwin else "MONO_LINUX")
 
@@ -193,20 +222,33 @@ def build_extension(self, ext):
         if DEVTOOLS == "MsDev":
             _xbuild = '"{0}"'.format(self._find_msbuild_tool("msbuild.exe"))
             _config = "{0}Win".format(CONFIG)
-
+            _solution_file = 'pythonnet.sln'
+            _custom_define_constants = False
+        elif DEVTOOLS == "MsDev15":
+            _xbuild = '"{0}"'.format(self._find_msbuild_tool_15()) 
+            _config = "{0}Win".format(CONFIG)
+            _solution_file = 'pythonnet.15.sln'
+            _custom_define_constants = True
         elif DEVTOOLS == "Mono":
-            _xbuild = "xbuild"
+            _xbuild = 'xbuild'
             _config = "{0}Mono".format(CONFIG)
+            _solution_file = 'pythonnet.sln'
+            _custom_define_constants = False
+        elif DEVTOOLS == "dotnet":
+            _xbuild = 'dotnet msbuild'
+            _config = "{0}Mono".format(CONFIG)
+            _solution_file = 'pythonnet.15.sln'
+            _custom_define_constants = True
         else:
             raise NotImplementedError(
-                "DevTool {0} not supported (use MsDev/Mono)".format(DEVTOOLS))
+                "DevTool {0} not supported (use MsDev/MsDev15/Mono/dotnet)".format(DEVTOOLS))
 
         cmd = [
             _xbuild,
-            'pythonnet.sln',
+            _solution_file,
             '/p:Configuration={}'.format(_config),
             '/p:Platform={}'.format(ARCH),
-            '/p:DefineConstants="{}"'.format(','.join(defines)),
+            '/p:{}DefineConstants="{}"'.format('Custom' if _custom_define_constants else '','%3B'.join(defines)),
             '/p:PythonBuildDir="{}"'.format(os.path.abspath(dest_dir)),
             '/p:PythonInteropFile="{}"'.format(os.path.basename(interop_file)),
             '/verbosity:{}'.format(VERBOSITY),
@@ -217,15 +259,17 @@ def build_extension(self, ext):
             cmd.append('/p:PythonManifest="{0}"'.format(manifest))
 
         self.debug_print("Building: {0}".format(" ".join(cmd)))
-        use_shell = True if DEVTOOLS == "Mono" else False
+        use_shell = True if DEVTOOLS == "Mono" or DEVTOOLS == "dotnet" else False
+
         subprocess.check_call(" ".join(cmd + ["/t:Clean"]), shell=use_shell)
         subprocess.check_call(" ".join(cmd + ["/t:Build"]), shell=use_shell)
-
-        if DEVTOOLS == "Mono":
+        if DEVTOOLS == "MsDev15" or DEVTOOLS == "dotnet":
+            subprocess.check_call(" ".join(cmd + ['"/t:Console_15:publish;Python_EmbeddingTest_15:publish"', "/p:TargetFramework=netcoreapp2.0"]), shell=use_shell)
+        if DEVTOOLS == "Mono" or DEVTOOLS == "dotnet":
             self._build_monoclr()
 
     def _get_manifest(self, build_dir):
-        if DEVTOOLS != "MsDev":
+        if DEVTOOLS != "MsDev" and DEVTOOLS != "MsDev15":
             return
         mt = self._find_msbuild_tool("mt.exe", use_windows_sdk=True)
         manifest = os.path.abspath(os.path.join(build_dir, "app.manifest"))
@@ -236,7 +280,13 @@ def _get_manifest(self, build_dir):
         return manifest
 
     def _build_monoclr(self):
-        mono_libs = _check_output("pkg-config --libs mono-2", shell=True)
+        try:
+            mono_libs = _check_output("pkg-config --libs mono-2", shell=True)
+        except:
+            if DEVTOOLS == "dotnet":
+                print("Skipping building monoclr module...")
+                return
+            raise
         mono_cflags = _check_output("pkg-config --cflags mono-2", shell=True)
         glib_libs = _check_output("pkg-config --libs glib-2.0", shell=True)
         glib_cflags = _check_output("pkg-config --cflags glib-2.0", shell=True)
@@ -258,22 +308,54 @@ def _build_monoclr(self):
 
     def _install_packages(self):
         """install packages using nuget"""
-        nuget = os.path.join("tools", "nuget", "nuget.exe")
-        use_shell = False
-        if DEVTOOLS == "Mono":
-            nuget = "mono {0}".format(nuget)
-            use_shell = True
+        use_shell = DEVTOOLS == "Mono" or DEVTOOLS == "dotnet"
+
+        if DEVTOOLS == "MsDev15" or DEVTOOLS == "dotnet":
+            if DEVTOOLS == "MsDev15":
+                _config = "{0}Win".format(CONFIG)
+            elif DEVTOOLS == "dotnet":
+                _config = "{0}Mono".format(CONFIG)
+
+            cmd = "dotnet msbuild /t:Restore pythonnet.15.sln /p:Configuration={0} /p:Platform={1}".format(_config, ARCH)
+            self.debug_print("Updating packages with xplat: {0}".format(cmd))
+            subprocess.check_call(cmd, shell=use_shell)
+        else:
+            nuget = os.path.join("tools", "nuget", "nuget.exe")
 
-        cmd = "{0} update -self".format(nuget)
-        self.debug_print("Updating NuGet: {0}".format(cmd))
-        subprocess.check_call(cmd, shell=use_shell)
+            if DEVTOOLS == "Mono":
+                nuget = "mono {0}".format(nuget)
 
-        cmd = "{0} restore pythonnet.sln -o packages".format(nuget)
-        self.debug_print("Installing packages: {0}".format(cmd))
-        subprocess.check_call(cmd, shell=use_shell)
+            cmd = "{0} update -self".format(nuget)
+            self.debug_print("Updating NuGet: {0}".format(cmd))
+            subprocess.check_call(cmd, shell=use_shell)
+
+            try:
+                # msbuild=14 is mainly for Mono issues
+                cmd = "{0} restore pythonnet.sln  -MSBuildVersion 14 -o packages".format(nuget)
+                self.debug_print("Installing packages: {0}".format(cmd))
+                subprocess.check_call(cmd, shell=use_shell)
+            except:
+                # when only VS 2017 is installed do not specify msbuild version
+                cmd = "{0} restore pythonnet.sln  -o packages".format(nuget)
+                self.debug_print("Installing packages: {0}".format(cmd))
+                subprocess.check_call(cmd, shell=use_shell)
 
     def _find_msbuild_tool(self, tool="msbuild.exe", use_windows_sdk=False):
         """Return full path to one of the Microsoft build tools"""
+
+        # trying to search path with help of vswhere when MSBuild 15.0 and higher installed.
+        if tool=="msbuild.exe" and use_windows_sdk==False:
+            try:
+                basePathes = subprocess.check_output(
+                    ["tools\\vswhere\\vswhere.exe", "-latest",
+                     "-version", "[15.0, 16.0)", 
+                     "-requires", "Microsoft.Component.MSBuild",
+                     "-property", "InstallationPath"]).splitlines()
+                if len(basePathes):
+                    return os.path.join(basePathes[0].decode(sys.stdout.encoding or "utf-8"), "MSBuild", "15.0", "Bin", "MSBuild.exe")
+            except:
+                pass # keep trying to search by old method.
+
         # Search in PATH first
         path = spawn.find_executable(tool)
         if path:
@@ -316,6 +398,20 @@ def _find_msbuild_tool(self, tool="msbuild.exe", use_windows_sdk=False):
 
         raise RuntimeError("{0} could not be found".format(tool))
 
+    def _find_msbuild_tool_15(self):
+        """Return full path to one of the Microsoft build tools"""
+        try:
+            basePathes = subprocess.check_output(
+                ["tools\\vswhere\\vswhere.exe", "-latest",
+                 "-version", "[15.0, 16.0)", 
+                 "-requires", "Microsoft.Component.MSBuild",
+                 "-property", "InstallationPath"]).splitlines()
+            if len(basePathes):
+                return os.path.join(basePathes[0].decode(sys.stdout.encoding or "utf-8"), "MSBuild", "15.0", "Bin", "MSBuild.exe")
+            else:
+                raise RuntimeError("MSBuild >=15.0 could not be found.")
+        except subprocess.CalledProcessError as e:
+            raise RuntimeError("MSBuild >=15.0 could not be found. {0}".format(e.output))
 
 class InstallLibPythonnet(install_lib.install_lib):
     def install(self):
@@ -353,8 +449,39 @@ def run(self):
 
         return install_data.install_data.run(self)
 
+class InstallPythonnet(install.install):
+    user_options = install.install.user_options + [
+            ('xplat', None, None)
+        ]
+    def initialize_options(self):
+        install.install.initialize_options(self)
+        self.xplat = None
 
-###############################################################################
+    def finalize_options(self):
+        install.install.finalize_options(self)
+
+    def run(self):
+        if self.xplat:
+            _update_xlat_devtools()
+        return install.install.run(self)
+
+class BDistWheelPythonnet(bdist_wheel.bdist_wheel):
+    user_options = bdist_wheel.bdist_wheel.user_options + [
+            ('xplat', None, None)
+        ]
+    def initialize_options(self):
+        bdist_wheel.bdist_wheel.initialize_options(self)
+        self.xplat = None
+
+    def finalize_options(self):
+        bdist_wheel.bdist_wheel.finalize_options(self)
+
+    def run(self):
+        if self.xplat:
+            _update_xlat_devtools()
+        return bdist_wheel.bdist_wheel.run(self)
+
+        ###############################################################################
 setupdir = os.path.dirname(__file__)
 if setupdir:
     os.chdir(setupdir)
@@ -365,7 +492,7 @@ def run(self):
 
 setup(
     name="pythonnet",
-    version="2.3.0",
+    version="2.4.0.dev0",
     description=".Net and Mono integration for Python",
     url='https://pythonnet.github.io/',
     license='MIT',
@@ -382,9 +509,11 @@ def run(self):
         ]),
     ],
     cmdclass={
+        "install": InstallPythonnet,
         "build_ext": BuildExtPythonnet,
         "install_lib": InstallLibPythonnet,
         "install_data": InstallDataPythonnet,
+        "bdist_wheel": BDistWheelPythonnet
     },
     classifiers=[
         'Development Status :: 5 - Production/Stable',
@@ -394,10 +523,10 @@ def run(self):
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Operating System :: Microsoft :: Windows',
         'Operating System :: POSIX :: Linux',
         'Operating System :: MacOS :: MacOS X',
diff --git a/src/SharedAssemblyInfo.cs b/src/SharedAssemblyInfo.cs
index 24ba26862..c164e75d6 100644
--- a/src/SharedAssemblyInfo.cs
+++ b/src/SharedAssemblyInfo.cs
@@ -25,4 +25,4 @@
 // Version Information. Keeping it simple. May need to revisit for Nuget
 // See: https://codingforsmarties.wordpress.com/2016/01/21/how-to-version-assemblies-destined-for-nuget/
 // AssemblyVersion can only be numeric
-[assembly: AssemblyVersion("2.3.0")]
+[assembly: AssemblyVersion("2.4.0")]
diff --git a/src/clrmodule/ClrModule.cs b/src/clrmodule/ClrModule.cs
index d24376a1f..3bb3a533b 100644
--- a/src/clrmodule/ClrModule.cs
+++ b/src/clrmodule/ClrModule.cs
@@ -53,7 +53,7 @@ public static void initclr()
         {
 #if USE_PYTHON_RUNTIME_VERSION
             // Has no effect until SNK works. Keep updated anyways.
-            Version = new Version("2.3.0"),
+            Version = new Version("2.4.0"),
 #endif
             CultureInfo = CultureInfo.InvariantCulture
         };
diff --git a/src/clrmodule/clrmodule.15.csproj b/src/clrmodule/clrmodule.15.csproj
new file mode 100644
index 000000000..2585ffdd2
--- /dev/null
+++ b/src/clrmodule/clrmodule.15.csproj
@@ -0,0 +1,95 @@
+<Project>
+
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetFrameworks>net40</TargetFrameworks>
+    <Platforms>x64;x86</Platforms>
+    <Configurations>DebugMono;DebugMonoPY3;ReleaseMono;ReleaseMonoPY3;DebugWin;DebugWinPY3;ReleaseWin;ReleaseWinPY3</Configurations>
+    <RootNamespace>clrmodule</RootNamespace>
+    <AssemblyName>clrmodule</AssemblyName>
+    <PackageId>clrmodule</PackageId>
+    <VersionPrefix>2.4.0</VersionPrefix>
+    <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
+    <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
+    <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
+    <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
+    <GenerateAssemblyDescriptionAttribute>false</GenerateAssemblyDescriptionAttribute>
+    <DocumentationFile>bin\clrmodule.xml</DocumentationFile>
+    <OutputPath>bin\</OutputPath>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <NoWarn>1591</NoWarn>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <PythonBuildDir Condition=" '$(PythonBuildDir)' == '' ">$(SolutionDir)\bin\</PythonBuildDir>
+    <PythonBuildDir Condition="'$(TargetFramework)'!='net40'">$(PythonBuildDir)\$(TargetFramework)\</PythonBuildDir>
+    <LangVersion>6</LangVersion>
+    <ErrorReport>prompt</ErrorReport>
+    <CustomDefineConstants Condition="'$(CustomDefineConstants)' == ''">$(PYTHONNET_DEFINE_CONSTANTS)</CustomDefineConstants>
+    <BaseDefineConstants>XPLAT</BaseDefineConstants>
+    <DefineConstants>$(DefineConstants);$(CustomDefineConstants);$(BaseDefineConstants);</DefineConstants>
+    <DefineConstants Condition="'$(BuildingInsideVisualStudio)' == 'true' AND '$(CustomDefineConstants)' != '' AND $(Configuration.Contains('Debug'))">$(DefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Platform)' == 'x86'">
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x64'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugMono'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMono'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugWin'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWin'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugMonoPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMonoPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugWinPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWinPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3</DefineConstants>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\SharedAssemblyInfo.cs" Link="Properties\SharedAssemblyInfo.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="UnmanagedExports" Version="1.2.7" />
+  </ItemGroup>
+
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetAssembly>$(TargetPath)</TargetAssembly>
+    <TargetAssemblyPdb>$(TargetDir)$(TargetName).pdb</TargetAssemblyPdb>
+  </PropertyGroup>
+
+  <Target Name="AfterBuild" DependsOnTargets="RGieseckeDllExport">
+    <Copy SourceFiles="$(TargetAssembly)" DestinationFiles="$(PythonBuildDir)\clr.pyd" />
+    <Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFiles="$(PythonBuildDir)\clr.pdb" />
+  </Target>
+  <Import Project="$(NuGetPackageRoot)/unmanagedexports/1.2.7/tools/RGiesecke.DllExport.targets" Condition="Exists('$(NuGetPackageRoot)/unmanagedexports/1.2.7/tools/RGiesecke.DllExport.targets')" />
+</Project>
diff --git a/src/console/Console.15.csproj b/src/console/Console.15.csproj
new file mode 100644
index 000000000..ec5008036
--- /dev/null
+++ b/src/console/Console.15.csproj
@@ -0,0 +1,94 @@
+<Project>
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+  <PropertyGroup>
+    <TargetFrameworks>net40;netcoreapp2.0</TargetFrameworks>
+    <Platforms>x64;x86</Platforms>
+    <Configurations>DebugMono;DebugMonoPY3;ReleaseMono;ReleaseMonoPY3;DebugWin;DebugWinPY3;ReleaseWin;ReleaseWinPY3</Configurations>
+    <OutputType>Exe</OutputType>
+    <AssemblyName>nPython</AssemblyName>
+    <RootNamespace>Python.Runtime</RootNamespace>
+    <PackageId>nPython</PackageId>
+    <VersionPrefix>2.4.0</VersionPrefix>
+    <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
+    <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
+    <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
+    <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
+    <GenerateAssemblyDescriptionAttribute>false</GenerateAssemblyDescriptionAttribute>
+    <OutputPath>bin\</OutputPath>
+    <AppendTargetFrameworkToOutputPath Condition="'$(TargetFramework)'=='net40'">false</AppendTargetFrameworkToOutputPath>
+    <DocumentationFile Condition="'$(TargetFramework)'=='net40'">$(OutputPath)\$(AssemblyName).xml</DocumentationFile>
+    <DocumentationFile Condition="'$(TargetFramework)'!='net40'">$(OutputPath)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
+    <NoWarn>1591</NoWarn>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <PythonBuildDir Condition=" '$(PythonBuildDir)' == '' ">$(SolutionDir)\bin\</PythonBuildDir>
+    <PublishDir Condition="'$(TargetFramework)'!='net40'">$(PythonBuildDir)\$(TargetFramework)\</PublishDir>
+    <LangVersion>6</LangVersion>
+    <ApplicationIcon>python-clear.ico</ApplicationIcon>
+    <ErrorReport>prompt</ErrorReport>
+    <CustomDefineConstants Condition="'$(CustomDefineConstants)' == ''">$(PYTHONNET_DEFINE_CONSTANTS)</CustomDefineConstants>
+    <BaseDefineConstants>XPLAT</BaseDefineConstants>
+    <DefineConstants>$(DefineConstants);$(CustomDefineConstants);$(BaseDefineConstants);</DefineConstants>
+    <DefineConstants Condition="'$(BuildingInsideVisualStudio)' == 'true' AND '$(CustomDefineConstants)' != '' AND $(Configuration.Contains('Debug'))">$(DefineConstants);TRACE;DEBUG</DefineConstants>
+    <FrameworkPathOverride Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono'))">$(NuGetPackageRoot)\microsoft.targetingpack.netframework.v4.5\1.0.1\lib\net45\</FrameworkPathOverride>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x86'">
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x64'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>true</Optimize>
+    <DebugType>portable</DebugType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);DEBUG;TRACE</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants)</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(PythonManifest)' != ''">
+    <ApplicationManifest>$(PythonManifest)</ApplicationManifest>
+  </PropertyGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <Reference Include="System" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="..\SharedAssemblyInfo.cs">
+      <Link>Properties\SharedAssemblyInfo.cs</Link>
+    </Compile>
+  </ItemGroup>
+  <ItemGroup>
+    <Content Include="python-clear.ico" />
+    <EmbeddedResource Condition="'$(TargetFramework)'=='net40'" Include="$(PythonBuildDir)\Python.Runtime.dll">
+      <LogicalName>Python.Runtime.dll</LogicalName>
+    </EmbeddedResource>
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\runtime\Python.Runtime.15.csproj" />
+  </ItemGroup>
+
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+  <Target Name="AfterBuild">
+    <Copy Condition="'$(TargetFramework)'=='net40'" SourceFiles="$(TargetPath)" DestinationFolder="$(PythonBuildDir)" />
+  </Target>
+</Project>
diff --git a/src/console/pythonconsole.cs b/src/console/pythonconsole.cs
index e9bb31e69..912e9bb0d 100644
--- a/src/console/pythonconsole.cs
+++ b/src/console/pythonconsole.cs
@@ -16,8 +16,9 @@ namespace Python.Runtime
     /// </remarks>
     public sealed class PythonConsole
     {
+#if NET40
         private static AssemblyLoader assemblyLoader = new AssemblyLoader();
-
+#endif
         private PythonConsole()
         {
         }
@@ -25,9 +26,11 @@ private PythonConsole()
         [STAThread]
         public static int Main(string[] args)
         {
+            // Only net40 is capable to safely inject python.runtime.dll into resources.
+#if NET40
             // reference the static assemblyLoader to stop it being optimized away
             AssemblyLoader a = assemblyLoader;
-
+#endif
             string[] cmd = Environment.GetCommandLineArgs();
             PythonEngine.Initialize();
 
@@ -37,6 +40,7 @@ public static int Main(string[] args)
             return i;
         }
 
+#if NET40
         // Register a callback function to load embedded assemblies.
         // (Python.Runtime.dll is included as a resource)
         private sealed class AssemblyLoader
@@ -73,5 +77,6 @@ public AssemblyLoader()
                 };
             }
         }
+#endif
     }
 }
diff --git a/src/embed_tests/GlobalTestsSetup.cs b/src/embed_tests/GlobalTestsSetup.cs
new file mode 100644
index 000000000..458ab6a99
--- /dev/null
+++ b/src/embed_tests/GlobalTestsSetup.cs
@@ -0,0 +1,21 @@
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+
+    // As the SetUpFixture, the OneTimeTearDown of this class is executed after
+    // all tests have run.
+    [SetUpFixture]
+    public class GlobalTestsSetup
+    {
+        [OneTimeTearDown]
+        public void FinalCleanup()
+        {
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+        }
+    }
+}
diff --git a/src/embed_tests/Program.cs b/src/embed_tests/Program.cs
new file mode 100644
index 000000000..b4439e3e4
--- /dev/null
+++ b/src/embed_tests/Program.cs
@@ -0,0 +1,19 @@
+using System;
+
+using NUnit.Common;
+
+using NUnitLite;
+
+namespace Python.EmbeddingTest
+{
+    public class Program
+    {
+        public static int Main(string[] args)
+        {
+            return new AutoRun(typeof(Program).Assembly).Execute(
+                args,
+                new ExtendedTextWrapper(Console.Out),
+                Console.In);
+        }
+    }
+}
diff --git a/src/embed_tests/Python.EmbeddingTest.15.csproj b/src/embed_tests/Python.EmbeddingTest.15.csproj
new file mode 100644
index 000000000..a741a589e
--- /dev/null
+++ b/src/embed_tests/Python.EmbeddingTest.15.csproj
@@ -0,0 +1,116 @@
+<Project>
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetFrameworks>net40;netcoreapp2.0</TargetFrameworks>
+    <Platforms>x64;x86</Platforms>
+    <Configurations>DebugMono;DebugMonoPY3;ReleaseMono;ReleaseMonoPY3;DebugWin;DebugWinPY3;ReleaseWin;ReleaseWinPY3</Configurations>
+    <OutputType Condition="'$(TargetFramework)' != 'net40' OR '$(PYTHONNET_VS_ENV)' == 'true'">Exe</OutputType>
+    <GenerateProgramFile>false</GenerateProgramFile>
+    <AssemblyName>Python.EmbeddingTest</AssemblyName>
+    <RootNamespace>Python.EmbeddingTest</RootNamespace>
+    <PackageId>Python.EmbeddingTest</PackageId>
+    <VersionPrefix>2.4.0</VersionPrefix>
+    <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
+    <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
+    <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
+    <OutputPath>bin\</OutputPath>
+    <AppendTargetFrameworkToOutputPath Condition="'$(TargetFramework)'=='net40'">false</AppendTargetFrameworkToOutputPath>
+    <DocumentationFile Condition="'$(TargetFramework)'=='net40'">$(OutputPath)\$(AssemblyName).xml</DocumentationFile>
+    <DocumentationFile Condition="'$(TargetFramework)'!='net40'">$(OutputPath)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
+    <NoWarn>1591</NoWarn>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <PythonBuildDir Condition="'$(TargetFramework)'=='net40' AND '$(PythonBuildDir)' == ''">$(SolutionDir)\bin\</PythonBuildDir>
+    <PublishDir Condition="'$(TargetFramework)'!='net40'">$(OutputPath)\$(TargetFramework)_publish</PublishDir>
+    <LangVersion>6</LangVersion>
+    <ErrorReport>prompt</ErrorReport>
+    <CustomDefineConstants Condition="'$(CustomDefineConstants)' == ''">$(PYTHONNET_DEFINE_CONSTANTS)</CustomDefineConstants>
+    <BaseDefineConstants>XPLAT</BaseDefineConstants>
+    <DefineConstants>$(DefineConstants);$(CustomDefineConstants);$(BaseDefineConstants);</DefineConstants>
+    <DefineConstants Condition="'$(TargetFramework)'=='netcoreapp2.0'">$(DefineConstants);NETCOREAPP</DefineConstants>
+    <DefineConstants Condition="'$(TargetFramework)'=='netstandard2.0'">$(DefineConstants);NETSTANDARD</DefineConstants>
+    <DefineConstants Condition="'$(BuildingInsideVisualStudio)' == 'true' AND '$(CustomDefineConstants)' != '' AND $(Configuration.Contains('Debug'))">$(DefineConstants);TRACE;DEBUG</DefineConstants>
+    <FrameworkPathOverride Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono'))">$(NuGetPackageRoot)\microsoft.targetingpack.netframework.v4.5\1.0.1\lib\net45\</FrameworkPathOverride>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x86'">
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x64'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>true</Optimize>
+    <DebugType>portable</DebugType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);DEBUG;TRACE</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants)</DefineConstants>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Include="..\pythonnet.snk" />
+    <None Remove="packages.config" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Include="..\SharedAssemblyInfo.cs" Link="Properties\SharedAssemblyInfo.cs" />
+  </ItemGroup>
+
+  
+  <ItemGroup>
+    <PackageReference Include="NUnit" Version="3.7.1" />
+    <PackageReference Include="NUnit.ConsoleRunner" Version="3.7.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="3.8.0" />
+    <PackageReference Include="NUnitLite" Version="3.7.2" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp2.0'">
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\runtime\Python.Runtime.15.csproj" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <Reference Include="Microsoft.CSharp" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Folder Include="Properties\" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Service Include="{82a7f48d-3b50-4b1e-b82e-3ada8210c358}" />
+  </ItemGroup>
+
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetAssembly>$(TargetPath)</TargetAssembly>
+    <TargetAssemblyPdb>$(TargetDir)$(TargetName).pdb</TargetAssemblyPdb>
+  </PropertyGroup>
+
+  <Target Name="AfterBuild">
+    <Copy Condition="'$(TargetFramework)'=='net40'" SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
+  </Target>
+
+</Project>
diff --git a/src/embed_tests/Python.EmbeddingTest.csproj b/src/embed_tests/Python.EmbeddingTest.csproj
index 9c417cd27..6aa48becc 100644
--- a/src/embed_tests/Python.EmbeddingTest.csproj
+++ b/src/embed_tests/Python.EmbeddingTest.csproj
@@ -70,8 +70,8 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="Microsoft.CSharp" />
-    <Reference Include="nunit.framework, Version=3.6.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb, processorArchitecture=MSIL">
-      <HintPath>..\..\packages\NUnit.3.6.0\lib\net40\nunit.framework.dll</HintPath>
+    <Reference Include="nunit.framework, Version=3.7.1.0, Culture=neutral, PublicKeyToken=2638cd05610744eb, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\NUnit.3.7.1\lib\net40\nunit.framework.dll</HintPath>
     </Reference>
     <Reference Include="System" />
   </ItemGroup>
@@ -84,19 +84,28 @@
     <Compile Include="pyimport.cs" />
     <Compile Include="pyinitialize.cs" />
     <Compile Include="pyrunstring.cs" />
+    <Compile Include="TestConverter.cs" />
     <Compile Include="TestCustomMarshal.cs" />
+    <Compile Include="TestDomainReload.cs" />
+    <Compile Include="TestExample.cs" />
     <Compile Include="TestPyAnsiString.cs" />
     <Compile Include="TestPyFloat.cs" />
     <Compile Include="TestPyInt.cs" />
     <Compile Include="TestPyList.cs" />
     <Compile Include="TestPyLong.cs" />
     <Compile Include="TestPyNumber.cs" />
+    <Compile Include="TestPyObject.cs" />
     <Compile Include="TestPySequence.cs" />
     <Compile Include="TestPyString.cs" />
     <Compile Include="TestPythonException.cs" />
     <Compile Include="TestPythonEngineProperties.cs" />
     <Compile Include="TestPyTuple.cs" />
+    <Compile Include="TestNamedArguments.cs" />
+    <Compile Include="TestPyWith.cs" />
     <Compile Include="TestRuntime.cs" />
+    <Compile Include="TestPyScope.cs" />
+    <Compile Include="TestTypeManager.cs" />
+    <Compile Include="GlobalTestsSetup.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\runtime\Python.Runtime.csproj">
@@ -114,6 +123,6 @@
   </PropertyGroup>
   <Target Name="AfterBuild">
     <Copy SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
-    <Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
   </Target>
 </Project>
diff --git a/src/embed_tests/TestConverter.cs b/src/embed_tests/TestConverter.cs
new file mode 100644
index 000000000..caaec311b
--- /dev/null
+++ b/src/embed_tests/TestConverter.cs
@@ -0,0 +1,48 @@
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class TestConverter
+    {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            PythonEngine.Initialize();
+        }
+
+        [OneTimeTearDown]
+        public void Dispose()
+        {
+            PythonEngine.Shutdown();
+        }
+
+        [Test]
+        public void TestConvertSingleToManaged(
+            [Values(float.PositiveInfinity, float.NegativeInfinity, float.MinValue, float.MaxValue, float.NaN,
+                float.Epsilon)] float testValue)
+        {
+            var pyFloat = new PyFloat(testValue);
+
+            object convertedValue;
+            var converted = Converter.ToManaged(pyFloat.Handle, typeof(float), out convertedValue, false);
+
+            Assert.IsTrue(converted);
+            Assert.IsTrue(((float) convertedValue).Equals(testValue));
+        }
+
+        [Test]
+        public void TestConvertDoubleToManaged(
+            [Values(double.PositiveInfinity, double.NegativeInfinity, double.MinValue, double.MaxValue, double.NaN,
+                double.Epsilon)] double testValue)
+        {
+            var pyFloat = new PyFloat(testValue);
+
+            object convertedValue;
+            var converted = Converter.ToManaged(pyFloat.Handle, typeof(double), out convertedValue, false);
+
+            Assert.IsTrue(converted);
+            Assert.IsTrue(((double) convertedValue).Equals(testValue));
+        }
+    }
+}
diff --git a/src/embed_tests/TestDomainReload.cs b/src/embed_tests/TestDomainReload.cs
new file mode 100644
index 000000000..b162d4eb0
--- /dev/null
+++ b/src/embed_tests/TestDomainReload.cs
@@ -0,0 +1,239 @@
+using System;
+using System.CodeDom.Compiler;
+using System.Reflection;
+using NUnit.Framework;
+using Python.Runtime;
+
+//
+// This test case is disabled on .NET Standard because it doesn't have all the
+// APIs we use. We could work around that, but .NET Core doesn't implement
+// domain creation, so it's not worth it.
+//
+// Unfortunately this means no continuous integration testing for this case.
+//
+#if !NETSTANDARD && !NETCOREAPP
+namespace Python.EmbeddingTest
+{
+    class TestDomainReload
+    {
+        /// <summary>
+        /// Test that the python runtime can survive a C# domain reload without crashing.
+        ///
+        /// At the time this test was written, there was a very annoying
+        /// seemingly random crash bug when integrating pythonnet into Unity.
+        ///
+        /// The repro steps that David Lassonde, Viktoria Kovecses and
+        /// Benoit Hudson eventually worked out:
+        /// 1. Write a HelloWorld.cs script that uses Python.Runtime to access
+        ///     some C# data from python: C# calls python, which calls C#.
+        /// 2. Execute the script (e.g. make it a MenuItem and click it).
+        /// 3. Touch HelloWorld.cs on disk, forcing Unity to recompile scripts.
+        /// 4. Wait several seconds for Unity to be done recompiling and
+        ///     reloading the C# domain.
+        /// 5. Make python run the gc (e.g. by calling gc.collect()).
+        ///
+        /// The reason:
+        /// A. In step 2, Python.Runtime registers a bunch of new types with
+        ///     their tp_traverse slot pointing to managed code, and allocates
+        ///     some objects of those types.
+        /// B. In step 4, Unity unloads the C# domain. That frees the managed
+        ///     code. But at the time of the crash investigation, pythonnet
+        ///     leaked the python side of the objects allocated in step 1.
+        /// C. In step 5, python sees some pythonnet objects in its gc list of
+        ///     potentially-leaked objects. It calls tp_traverse on those objects.
+        ///     But tp_traverse was freed in step 3 => CRASH.
+        ///
+        /// This test distills what's going on without needing Unity around (we'd see
+        /// similar behaviour if we were using pythonnet on a .NET web server that did
+        /// a hot reload).
+        /// </summary>
+        [Test]
+        public static void DomainReloadAndGC()
+        {
+            // We're set up to run in the directory that includes the bin directory.
+            System.IO.Directory.SetCurrentDirectory(AppDomain.CurrentDomain.BaseDirectory);
+
+            Assembly pythonRunner1 = BuildAssembly("test1");
+            RunAssemblyAndUnload(pythonRunner1, "test1");
+
+            // Verify that python is not initialized even though we ran it.
+            Assert.That(Runtime.Runtime.Py_IsInitialized(), Is.Zero);
+
+            // This caused a crash because objects allocated in pythonRunner1
+            // still existed in memory, but the code to do python GC on those
+            // objects is gone.
+            Assembly pythonRunner2 = BuildAssembly("test2");
+            RunAssemblyAndUnload(pythonRunner2, "test2");
+        }
+
+        //
+        // The code we'll test. All that really matters is
+        //    using GIL { Python.Exec(pyScript); }
+        // but the rest is useful for debugging.
+        //
+        // What matters in the python code is gc.collect and clr.AddReference.
+        //
+        // Note that the language version is 2.0, so no $"foo{bar}" syntax.
+        //
+        const string TestCode = @"
+            using Python.Runtime;
+            using System;
+            class PythonRunner {
+                public static void RunPython() {
+                    AppDomain.CurrentDomain.DomainUnload += OnDomainUnload;
+                    string name = AppDomain.CurrentDomain.FriendlyName;
+                    Console.WriteLine(string.Format(""[{0} in .NET] In PythonRunner.RunPython"", name));
+                    using (Py.GIL()) {
+                        try {
+                            var pyScript = string.Format(""import clr\n""
+                                + ""print('[{0} in python] imported clr')\n""
+                                + ""clr.AddReference('System')\n""
+                                + ""print('[{0} in python] allocated a clr object')\n""
+                                + ""import gc\n""
+                                + ""gc.collect()\n""
+                                + ""print('[{0} in python] collected garbage')\n"",
+                                name);
+                            PythonEngine.Exec(pyScript);
+                        } catch(Exception e) {
+                            Console.WriteLine(string.Format(""[{0} in .NET] Caught exception: {1}"", name, e));
+                        }
+                    }
+                }
+                static void OnDomainUnload(object sender, EventArgs e) {
+                    System.Console.WriteLine(string.Format(""[{0} in .NET] unloading"", AppDomain.CurrentDomain.FriendlyName));
+                }
+            }";
+
+
+        /// <summary>
+        /// Build an assembly out of the source code above.
+        ///
+        /// This creates a file <paramref name="assemblyName"/>.dll in order
+        /// to support the statement "proxy.theAssembly = assembly" below.
+        /// That statement needs a file, can't run via memory.
+        /// </summary>
+        static Assembly BuildAssembly(string assemblyName)
+        {
+            var provider = CodeDomProvider.CreateProvider("CSharp");
+
+            var compilerparams = new CompilerParameters();
+            compilerparams.ReferencedAssemblies.Add("Python.Runtime.dll");
+            compilerparams.GenerateExecutable = false;
+            compilerparams.GenerateInMemory = false;
+            compilerparams.IncludeDebugInformation = false;
+            compilerparams.OutputAssembly = assemblyName;
+
+            var results = provider.CompileAssemblyFromSource(compilerparams, TestCode);
+            if (results.Errors.HasErrors)
+            {
+                var errors = new System.Text.StringBuilder("Compiler Errors:\n");
+                foreach (CompilerError error in results.Errors)
+                {
+                    errors.AppendFormat("Line {0},{1}\t: {2}\n",
+                            error.Line, error.Column, error.ErrorText);
+                }
+                throw new Exception(errors.ToString());
+            }
+            else
+            {
+                return results.CompiledAssembly;
+            }
+        }
+
+        /// <summary>
+        /// This is a magic incantation required to run code in an application
+        /// domain other than the current one.
+        /// </summary>
+        class Proxy : MarshalByRefObject
+        {
+            Assembly theAssembly = null;
+
+            public void InitAssembly(string assemblyPath)
+            {
+                theAssembly = Assembly.LoadFile(System.IO.Path.GetFullPath(assemblyPath));
+            }
+
+            public void RunPython()
+            {
+                Console.WriteLine("[Proxy] Entering RunPython");
+
+                // Call into the new assembly. Will execute Python code
+                var pythonrunner = theAssembly.GetType("PythonRunner");
+                var runPythonMethod = pythonrunner.GetMethod("RunPython");
+                runPythonMethod.Invoke(null, new object[] { });
+
+                Console.WriteLine("[Proxy] Leaving RunPython");
+            }
+        }
+
+        /// <summary>
+        /// Create a domain, run the assembly in it (the RunPython function),
+        /// and unload the domain.
+        /// </summary>
+        static void RunAssemblyAndUnload(Assembly assembly, string assemblyName)
+        {
+            Console.WriteLine($"[Program.Main] === creating domain for assembly {assembly.FullName}");
+
+            // Create the domain. Make sure to set PrivateBinPath to a relative
+            // path from the CWD (namely, 'bin').
+            // See https://stackoverflow.com/questions/24760543/createinstanceandunwrap-in-another-domain
+            var currentDomain = AppDomain.CurrentDomain;
+            var domainsetup = new AppDomainSetup()
+            {
+                ApplicationBase = currentDomain.SetupInformation.ApplicationBase,
+                ConfigurationFile = currentDomain.SetupInformation.ConfigurationFile,
+                LoaderOptimization = LoaderOptimization.SingleDomain,
+                PrivateBinPath = "."
+            };
+            var domain = AppDomain.CreateDomain(
+                    $"My Domain {assemblyName}",
+                    currentDomain.Evidence,
+                domainsetup);
+
+            // Create a Proxy object in the new domain, where we want the
+            // assembly (and Python .NET) to reside
+            Type type = typeof(Proxy);
+            System.IO.Directory.SetCurrentDirectory(AppDomain.CurrentDomain.BaseDirectory);
+            var theProxy = (Proxy)domain.CreateInstanceAndUnwrap(
+                    type.Assembly.FullName,
+                    type.FullName);
+
+            // From now on use the Proxy to call into the new assembly
+            theProxy.InitAssembly(assemblyName);
+            theProxy.RunPython();
+
+            Console.WriteLine($"[Program.Main] Before Domain Unload on {assembly.FullName}");
+            AppDomain.Unload(domain);
+            Console.WriteLine($"[Program.Main] After Domain Unload on {assembly.FullName}");
+
+            // Validate that the assembly does not exist anymore
+            try
+            {
+                Console.WriteLine($"[Program.Main] The Proxy object is valid ({theProxy}). Unexpected domain unload behavior");
+            }
+            catch (Exception)
+            {
+                Console.WriteLine("[Program.Main] The Proxy object is not valid anymore, domain unload complete.");
+            }
+        }
+
+        /// <summary>
+        /// Resolves the assembly. Why doesn't this just work normally?
+        /// </summary>
+        static Assembly ResolveAssembly(object sender, ResolveEventArgs args)
+        {
+            var loadedAssemblies = AppDomain.CurrentDomain.GetAssemblies();
+
+            foreach (var assembly in loadedAssemblies)
+            {
+                if (assembly.FullName == args.Name)
+                {
+                    return assembly;
+                }
+            }
+
+            return null;
+        }
+    }
+}
+#endif
diff --git a/src/embed_tests/TestExample.cs b/src/embed_tests/TestExample.cs
new file mode 100644
index 000000000..671f9e33d
--- /dev/null
+++ b/src/embed_tests/TestExample.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class TestExample
+    {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            PythonEngine.Initialize();
+        }
+
+        [OneTimeTearDown]
+        public void Dispose()
+        {
+            PythonEngine.Shutdown();
+        }
+
+        [Test]
+        public void TestReadme()
+        {
+            dynamic np;
+            try
+            {
+                np = Py.Import("numpy");
+            }
+            catch (PythonException)
+            {
+                Assert.Inconclusive("Numpy or dependency not installed");
+                return;
+            }
+            
+            Assert.AreEqual("1.0", np.cos(np.pi * 2).ToString());
+
+            dynamic sin = np.sin;
+            StringAssert.StartsWith("-0.95892", sin(5).ToString());
+
+            double c = np.cos(5) + sin(5);
+            Assert.AreEqual(-0.675262, c, 0.01);
+
+            dynamic a = np.array(new List<float> { 1, 2, 3 });
+            Assert.AreEqual("float64", a.dtype.ToString());
+
+            dynamic b = np.array(new List<float> { 6, 5, 4 }, Py.kw("dtype", np.int32));
+            Assert.AreEqual("int32", b.dtype.ToString());
+
+            Assert.AreEqual("[ 6. 10. 12.]", (a * b).ToString().Replace("  ", " "));
+        }
+    }
+}
diff --git a/src/embed_tests/TestNamedArguments.cs b/src/embed_tests/TestNamedArguments.cs
new file mode 100644
index 000000000..31f2ea1d2
--- /dev/null
+++ b/src/embed_tests/TestNamedArguments.cs
@@ -0,0 +1,64 @@
+using System;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class TestNamedArguments
+    {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            PythonEngine.Initialize();
+        }
+
+        [OneTimeTearDown]
+        public void Dispose()
+        {
+            PythonEngine.Shutdown();
+        }
+
+        /// <summary>
+        /// Test named arguments support through Py.kw method
+        /// </summary>
+        [Test]
+        public void TestKeywordArgs()
+        {
+            dynamic a = CreateTestClass();
+            var result = (int)a.Test3(2, Py.kw("a4", 8));
+
+            Assert.AreEqual(12, result);
+        }
+
+
+        /// <summary>
+        /// Test keyword arguments with .net named arguments
+        /// </summary>
+        [Test]
+        public void TestNamedArgs()
+        {
+            dynamic a = CreateTestClass();
+            var result = (int)a.Test3(2, a4: 8);
+
+            Assert.AreEqual(12, result);
+        }
+
+
+
+        private static PyObject CreateTestClass()
+        {
+            var locals = new PyDict();
+
+            PythonEngine.Exec(@"
+class cmTest3:
+    def Test3(self, a1 = 1, a2 = 1, a3 = 1, a4 = 1):
+        return a1 + a2 + a3 + a4
+
+a = cmTest3()
+", null, locals.Handle);
+
+            return locals.GetItem("a");
+        }
+
+    }
+}
diff --git a/src/embed_tests/TestPyObject.cs b/src/embed_tests/TestPyObject.cs
new file mode 100644
index 000000000..65ac20e9a
--- /dev/null
+++ b/src/embed_tests/TestPyObject.cs
@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class TestPyObject
+    {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            PythonEngine.Initialize();
+        }
+
+        [OneTimeTearDown]
+        public void Dispose()
+        {
+            PythonEngine.Shutdown();
+        }
+
+        [Test]
+        public void TestGetDynamicMemberNames()
+        {
+            List<string> expectedMemberNames = new List<string>
+            {
+                "add",
+                "getNumber",
+                "member1",
+                "member2"
+            };
+
+            PyDict locals = new PyDict();
+
+            PythonEngine.Exec(@"
+class MemberNamesTest(object):
+    def __init__(self):
+        self.member1 = 123
+        self.member2 = 'Test string'
+
+    def getNumber(self):
+        return 123
+
+    def add(self, x, y):
+        return x + y
+
+a = MemberNamesTest()
+", null, locals.Handle);
+
+            PyObject a = locals.GetItem("a");
+
+            IEnumerable<string> memberNames = a.GetDynamicMemberNames();
+
+            foreach (string expectedName in expectedMemberNames)
+            {
+                Assert.IsTrue(memberNames.Contains(expectedName), "Could not find member '{0}'.", expectedName);
+            }
+        }
+    }
+}
diff --git a/src/embed_tests/TestPyScope.cs b/src/embed_tests/TestPyScope.cs
new file mode 100644
index 000000000..49c15a3a1
--- /dev/null
+++ b/src/embed_tests/TestPyScope.cs
@@ -0,0 +1,372 @@
+using System;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class PyScopeTest
+    {
+        private PyScope ps;
+
+        [SetUp]
+        public void SetUp()
+        {
+            using (Py.GIL())
+            {
+                ps = Py.CreateScope("test");
+            }                
+        }
+
+        [TearDown]
+        public void Dispose()
+        {
+            using (Py.GIL())
+            {
+                ps.Dispose();
+                ps = null;
+            }
+        }
+
+        /// <summary>
+        /// Eval a Python expression and obtain its return value.
+        /// </summary>
+        [Test]
+        public void TestEval()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("a", 1);
+                var result = ps.Eval<int>("a + 2");
+                Assert.AreEqual(3, result);
+            }                
+        }
+
+        /// <summary>
+        /// Exec Python statements and obtain the variables created.
+        /// </summary>
+        [Test]
+        public void TestExec()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100); //declare a global variable
+                ps.Set("cc", 10); //declare a local variable
+                ps.Exec("aa = bb + cc + 3");
+                var result = ps.Get<int>("aa");
+                Assert.AreEqual(113, result);
+            }
+        }
+
+        /// <summary>
+        /// Compile an expression into an ast object;
+        /// Execute the ast and obtain its return value.
+        /// </summary>
+        [Test]
+        public void TestCompileExpression()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100); //declare a global variable
+                ps.Set("cc", 10); //declare a local variable
+                PyObject script = PythonEngine.Compile("bb + cc + 3", "", RunFlagType.Eval);
+                var result = ps.Execute<int>(script);
+                Assert.AreEqual(113, result);
+            }
+        }
+
+        /// <summary>
+        /// Compile Python statements into an ast object;
+        /// Execute the ast;
+        /// Obtain the local variables created.
+        /// </summary>
+        [Test]
+        public void TestCompileStatements()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100); //declare a global variable
+                ps.Set("cc", 10); //declare a local variable
+                PyObject script = PythonEngine.Compile("aa = bb + cc + 3", "", RunFlagType.File);
+                ps.Execute(script);
+                var result = ps.Get<int>("aa");
+                Assert.AreEqual(113, result);
+            }
+        }
+
+        /// <summary>
+        /// Create a function in the scope, then the function can read variables in the scope.
+        /// It cannot write the variables unless it uses the 'global' keyword.
+        /// </summary>
+        [Test]
+        public void TestScopeFunction()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100);
+                ps.Set("cc", 10);
+                ps.Exec(
+                    "def func1():\n" +
+                    "    bb = cc + 10\n");
+                dynamic func1 = ps.Get("func1");
+                func1(); //call the function, it can be called any times
+                var result = ps.Get<int>("bb");
+                Assert.AreEqual(100, result);
+
+                ps.Set("bb", 100);
+                ps.Set("cc", 10);
+                ps.Exec(
+                    "def func2():\n" +
+                    "    global bb\n" +
+                    "    bb = cc + 10\n");
+                dynamic func2 = ps.Get("func2");
+                func2();
+                result = ps.Get<int>("bb");
+                Assert.AreEqual(20, result);
+            }
+        }
+
+        /// <summary>
+        /// Create a class in the scope, the class can read variables in the scope.
+        /// Its methods can write the variables with the help of 'global' keyword.
+        /// </summary>
+        [Test]
+        public void TestScopeClass()
+        {
+            using (Py.GIL())
+            {
+                dynamic _ps = ps;
+                _ps.bb = 100;
+                ps.Exec(
+                    "class Class1():\n" +
+                    "    def __init__(self, value):\n" +
+                    "        self.value = value\n" +
+                    "    def call(self, arg):\n" +
+                    "        return self.value + bb + arg\n" + //use scope variables
+                    "    def update(self, arg):\n" +
+                    "        global bb\n" +
+                    "        bb = self.value + arg\n"  //update scope variable
+                );
+                dynamic obj1 = _ps.Class1(20);
+                var result = obj1.call(10).As<int>();
+                Assert.AreEqual(130, result);
+
+                obj1.update(10);
+                result = ps.Get<int>("bb");
+                Assert.AreEqual(30, result);
+            }
+        }
+
+        /// <summary>
+        /// Import a python module into the session.
+        /// Equivalent to the Python "import" statement.
+        /// </summary>
+        [Test]
+        public void TestImportModule()
+        {
+            using (Py.GIL())
+            {
+                dynamic sys = ps.Import("sys");
+                Assert.IsTrue(ps.Contains("sys"));
+
+                ps.Exec("sys.attr1 = 2");
+                var value1 = ps.Eval<int>("sys.attr1");
+                var value2 = sys.attr1.As<int>();
+                Assert.AreEqual(2, value1);
+                Assert.AreEqual(2, value2);
+
+                //import as
+                ps.Import("sys", "sys1");
+                Assert.IsTrue(ps.Contains("sys1"));
+            }
+        }
+
+        /// <summary>
+        /// Create a scope and import variables from a scope, 
+        /// exec Python statements in the scope then discard it.
+        /// </summary>
+        [Test]
+        public void TestImportScope()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100);
+                ps.Set("cc", 10);
+
+                using (var scope = Py.CreateScope())
+                {
+                    scope.Import(ps, "ps");
+                    scope.Exec("aa = ps.bb + ps.cc + 3");
+                    var result = scope.Get<int>("aa");
+                    Assert.AreEqual(113, result);
+                }
+
+                Assert.IsFalse(ps.Contains("aa"));
+            }
+        }
+
+        /// <summary>
+        /// Create a scope and import variables from a scope, 
+        /// exec Python statements in the scope then discard it.
+        /// </summary>
+        [Test]
+        public void TestImportAllFromScope()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100);
+                ps.Set("cc", 10);
+
+                using (var scope = ps.NewScope())
+                {
+                    scope.Exec("aa = bb + cc + 3");
+                    var result = scope.Get<int>("aa");
+                    Assert.AreEqual(113, result);
+                }
+
+                Assert.IsFalse(ps.Contains("aa"));
+            }
+        }
+
+        /// <summary>
+        /// Create a scope and import variables from a scope, 
+        /// call the function imported.
+        /// </summary>
+        [Test]
+        public void TestImportScopeFunction()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100);
+                ps.Set("cc", 10);
+                ps.Exec(
+                    "def func1():\n" +
+                    "    return cc + bb\n");
+
+                using (PyScope scope = ps.NewScope())
+                {
+                    //'func1' is imported from the origion scope
+                    scope.Exec(
+                        "def func2():\n" +
+                        "    return func1() - cc - bb\n");
+                    dynamic func2 = scope.Get("func2");
+
+                    var result1 = func2().As<int>();
+                    Assert.AreEqual(0, result1);
+
+                    scope.Set("cc", 20);//it has no effect on the globals of 'func1'
+                    var result2 = func2().As<int>();
+                    Assert.AreEqual(-10, result2);
+                    scope.Set("cc", 10); //rollback
+
+                    ps.Set("cc", 20);
+                    var result3 = func2().As<int>();
+                    Assert.AreEqual(10, result3);
+                    ps.Set("cc", 10); //rollback
+                }
+            }
+        }
+
+        /// <summary>
+        /// Import a python module into the session with a new name.
+        /// Equivalent to the Python "import .. as .." statement.
+        /// </summary>
+        [Test]
+        public void TestImportScopeByName()
+        {
+            using (Py.GIL())
+            {
+                ps.Set("bb", 100);
+
+                using (var scope = Py.CreateScope())
+                {
+                    scope.ImportAll("test");
+                    //scope.ImportModule("test");
+
+                    Assert.IsTrue(scope.Contains("bb"));
+                }                    
+            }
+        }
+
+        /// <summary>
+        /// Use the locals() and globals() method just like in python module
+        /// </summary>
+        [Test]
+        public void TestVariables()
+        {
+            (ps.Variables() as dynamic)["ee"] = new PyInt(200);
+            var a0 = ps.Get<int>("ee");
+            Assert.AreEqual(200, a0);
+
+            ps.Exec("locals()['ee'] = 210");
+            var a1 = ps.Get<int>("ee");
+            Assert.AreEqual(210, a1);
+
+            ps.Exec("globals()['ee'] = 220");
+            var a2 = ps.Get<int>("ee");
+            Assert.AreEqual(220, a2);
+
+            using (var item = ps.Variables())
+            {
+                item["ee"] = new PyInt(230);
+            }
+            var a3 = ps.Get<int>("ee");
+            Assert.AreEqual(230, a3);
+        }
+
+        /// <summary>
+        /// Share a pyscope by multiple threads.
+        /// </summary>
+        [Test]
+        public void TestThread()
+        {
+            //After the proposal here https://github.com/pythonnet/pythonnet/pull/419 complished,
+            //the BeginAllowThreads statement blow and the last EndAllowThreads statement
+            //should be removed.
+            dynamic _ps = ps;
+            var ts = PythonEngine.BeginAllowThreads();
+            using (Py.GIL())
+            {
+                _ps.res = 0;
+                _ps.bb = 100;
+                _ps.th_cnt = 0;
+                //add function to the scope 
+                //can be call many times, more efficient than ast 
+                ps.Exec(
+                    "def update():\n" +
+                    "    global res, th_cnt\n" +
+                    "    res += bb + 1\n" +
+                    "    th_cnt += 1\n"
+                );
+            }
+            int th_cnt = 3;
+            for (int i =0; i< th_cnt; i++)
+            {
+                System.Threading.Thread th = new System.Threading.Thread(()=>
+                {
+                    using (Py.GIL())
+                    {
+                        //ps.GetVariable<dynamic>("update")(); //call the scope function dynamicly
+                        _ps.update();
+                    }
+                });
+                th.Start();
+            }
+            //equivalent to Thread.Join, make the main thread join the GIL competition
+            int cnt = 0;
+            while(cnt != th_cnt)
+            {
+                using (Py.GIL())
+                {
+                    cnt = ps.Get<int>("th_cnt");
+                }
+                System.Threading.Thread.Sleep(10);
+            }
+            using (Py.GIL())
+            {
+                var result = ps.Get<int>("res");
+                Assert.AreEqual(101* th_cnt, result);
+            }
+            PythonEngine.EndAllowThreads(ts);
+        }
+    }
+}
diff --git a/src/embed_tests/TestPyWith.cs b/src/embed_tests/TestPyWith.cs
new file mode 100644
index 000000000..0c4e9023f
--- /dev/null
+++ b/src/embed_tests/TestPyWith.cs
@@ -0,0 +1,88 @@
+using System;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    public class TestPyWith
+    {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            PythonEngine.Initialize();
+        }
+
+        [OneTimeTearDown]
+        public void Dispose()
+        {
+            PythonEngine.Shutdown();
+        }
+
+        /// <summary>
+        /// Test that exception is raised in context manager that ignores it.
+        /// </summary>
+        [Test]
+        public void TestWithPositive()
+        {
+            var locals = new PyDict();
+            
+            PythonEngine.Exec(@"
+class CmTest:
+    def __enter__(self):
+        print('Enter')
+        return self
+    def __exit__(self, t, v, tb):
+        # Exception not handled, return will be False
+        print('Exit')
+    def fail(self):
+        return 5 / 0
+
+a = CmTest()
+", null, locals.Handle);
+
+            var a = locals.GetItem("a");
+
+            try
+            {
+                Py.With(a, cmTest =>
+                {
+                    cmTest.fail();
+                });
+            }
+            catch (PythonException e)
+            {
+                Assert.IsTrue(e.Message.Contains("ZeroDivisionError"));
+            }
+        }
+
+
+        /// <summary>
+        /// Test that exception is not raised in context manager that handles it
+        /// </summary>
+        [Test]
+        public void TestWithNegative()
+        {
+            var locals = new PyDict();
+
+            PythonEngine.Exec(@"
+class CmTest:
+    def __enter__(self):
+        print('Enter')
+        return self
+    def __exit__(self, t, v, tb):
+        # Signal exception is handled by returning true
+        return True
+    def fail(self):
+        return 5 / 0
+
+a = CmTest()
+", null, locals.Handle);
+
+            var a = locals.GetItem("a");
+            Py.With(a, cmTest =>
+            {
+                cmTest.fail();
+            });
+        }
+    }
+}
diff --git a/src/embed_tests/TestPythonEngineProperties.cs b/src/embed_tests/TestPythonEngineProperties.cs
index 01c6ae7e3..243349b82 100644
--- a/src/embed_tests/TestPythonEngineProperties.cs
+++ b/src/embed_tests/TestPythonEngineProperties.cs
@@ -109,18 +109,41 @@ public static void GetPythonHomeDefault()
         [Test]
         public void SetPythonHome()
         {
+            // We needs to ensure that engine was started and shutdown at least once before setting dummy home.
+            // Otherwise engine will not run with dummy path with random problem.
+            if (!PythonEngine.IsInitialized)
+            {
+                PythonEngine.Initialize();
+            }
+
+            PythonEngine.Shutdown();
+
+            var pythonHomeBackup = PythonEngine.PythonHome;
+
             var pythonHome = "/dummypath/";
 
             PythonEngine.PythonHome = pythonHome;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
             PythonEngine.Shutdown();
+
+            // Restoring valid pythonhome.
+            PythonEngine.PythonHome = pythonHomeBackup;
         }
 
         [Test]
         public void SetPythonHomeTwice()
         {
+            // We needs to ensure that engine was started and shutdown at least once before setting dummy home.
+            // Otherwise engine will not run with dummy path with random problem.
+            if (!PythonEngine.IsInitialized)
+            {
+                PythonEngine.Initialize();
+            }
+            PythonEngine.Shutdown();
+
+            var pythonHomeBackup = PythonEngine.PythonHome;
+
             var pythonHome = "/dummypath/";
 
             PythonEngine.PythonHome = "/dummypath2/";
@@ -129,11 +152,20 @@ public void SetPythonHomeTwice()
 
             Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
             PythonEngine.Shutdown();
+
+            PythonEngine.PythonHome = pythonHomeBackup;
         }
 
         [Test]
         public void SetProgramName()
         {
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+
+            var programNameBackup = PythonEngine.ProgramName;
+
             var programName = "FooBar";
 
             PythonEngine.ProgramName = programName;
@@ -141,6 +173,8 @@ public void SetProgramName()
 
             Assert.AreEqual(programName, PythonEngine.ProgramName);
             PythonEngine.Shutdown();
+
+            PythonEngine.ProgramName = programNameBackup;
         }
 
         [Test]
@@ -156,7 +190,7 @@ public void SetPythonPath()
             string path = PythonEngine.PythonPath;
             PythonEngine.Shutdown();
 
-            PythonEngine.ProgramName = path;
+            PythonEngine.PythonPath = path;
             PythonEngine.Initialize();
 
             Assert.AreEqual(path, PythonEngine.PythonPath);
@@ -171,7 +205,6 @@ public void SetPythonPathExceptionOn27()
                 Assert.Pass();
             }
 
-            // Get previous path to avoid crashing Python
             PythonEngine.Initialize();
             string path = PythonEngine.PythonPath;
             PythonEngine.Shutdown();
diff --git a/src/embed_tests/TestPythonException.cs b/src/embed_tests/TestPythonException.cs
index 5470b246f..57a8d54af 100644
--- a/src/embed_tests/TestPythonException.cs
+++ b/src/embed_tests/TestPythonException.cs
@@ -40,5 +40,19 @@ public void TestNoError()
             var e = new PythonException(); // There is no PyErr to fetch
             Assert.AreEqual("", e.Message);
         }
+
+        [Test]
+        public void TestPythonErrorTypeName()
+        {
+            try
+            {
+                var module = PythonEngine.ImportModule("really____unknown___module");
+                Assert.Fail("Unknown module should not be loaded");
+            }
+            catch (PythonException ex)
+            {
+                Assert.That(ex.PythonTypeName, Is.EqualTo("ModuleNotFoundError").Or.EqualTo("ImportError"));
+            }
+        }
     }
 }
diff --git a/src/embed_tests/TestRuntime.cs b/src/embed_tests/TestRuntime.cs
index 22e6db0a9..ac1fa1ac0 100644
--- a/src/embed_tests/TestRuntime.cs
+++ b/src/embed_tests/TestRuntime.cs
@@ -6,10 +6,40 @@ namespace Python.EmbeddingTest
 {
     public class TestRuntime
     {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            // We needs to ensure that no any engines are running.
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+        }
+
+        /// <summary>
+        /// Test the cache of the information from the platform module.
+        ///
+        /// Test fails on platforms we haven't implemented yet.
+        /// </summary>
+        [Test]
+        public static void PlatformCache()
+        {
+            Runtime.Runtime.Initialize();
+
+            Assert.That(Runtime.Runtime.Machine, Is.Not.EqualTo(Runtime.Runtime.MachineType.Other));
+            Assert.That(!string.IsNullOrEmpty(Runtime.Runtime.MachineName));
+
+            Assert.That(Runtime.Runtime.OperatingSystem, Is.Not.EqualTo(Runtime.Runtime.OperatingSystemType.Other));
+            Assert.That(!string.IsNullOrEmpty(Runtime.Runtime.OperatingSystemName));
+
+            // Don't shut down the runtime: if the python engine was initialized
+            // but not shut down by another test, we'd end up in a bad state.
+	}
+
         [Test]
         public static void Py_IsInitializedValue()
         {
-            Runtime.Runtime.Py_Finalize(); // In case another test left it on.
+            Runtime.Runtime.Py_Finalize(); 
             Assert.AreEqual(0, Runtime.Runtime.Py_IsInitialized());
             Runtime.Runtime.Py_Initialize();
             Assert.AreEqual(1, Runtime.Runtime.Py_IsInitialized());
@@ -47,5 +77,46 @@ public static void RefCountTest()
 
             Runtime.Runtime.Py_Finalize();
         }
+
+        [Test]
+        public static void PyCheck_Iter_PyObject_IsIterable_Test()
+        {
+            Runtime.Runtime.Py_Initialize();
+
+            // Tests that a python list is an iterable, but not an iterator
+            var pyList = Runtime.Runtime.PyList_New(0);
+            Assert.IsFalse(Runtime.Runtime.PyIter_Check(pyList));
+            Assert.IsTrue(Runtime.Runtime.PyObject_IsIterable(pyList));
+
+            // Tests that a python list iterator is both an iterable and an iterator
+            var pyListIter = Runtime.Runtime.PyObject_GetIter(pyList);
+            Assert.IsTrue(Runtime.Runtime.PyObject_IsIterable(pyListIter));
+            Assert.IsTrue(Runtime.Runtime.PyIter_Check(pyListIter));
+
+            // Tests that a python float is neither an iterable nor an iterator
+            var pyFloat = Runtime.Runtime.PyFloat_FromDouble(2.73);
+            Assert.IsFalse(Runtime.Runtime.PyObject_IsIterable(pyFloat));
+            Assert.IsFalse(Runtime.Runtime.PyIter_Check(pyFloat));
+
+            Runtime.Runtime.Py_Finalize();
+        }
+
+        [Test]
+        public static void PyCheck_Iter_PyObject_IsIterable_ThreadingLock_Test()
+        {
+            Runtime.Runtime.Py_Initialize();
+
+            // Create an instance of threading.Lock, which is one of the very few types that does not have the
+            // TypeFlags.HaveIter set in Python 2. This tests a different code path in PyObject_IsIterable and PyIter_Check.
+            var threading = Runtime.Runtime.PyImport_ImportModule("threading");
+            var threadingDict = Runtime.Runtime.PyModule_GetDict(threading);
+            var lockType = Runtime.Runtime.PyDict_GetItemString(threadingDict, "Lock");
+            var lockInstance = Runtime.Runtime.PyObject_CallObject(lockType, Runtime.Runtime.PyTuple_New(0));
+
+            Assert.IsFalse(Runtime.Runtime.PyObject_IsIterable(lockInstance));
+            Assert.IsFalse(Runtime.Runtime.PyIter_Check(lockInstance));
+
+            Runtime.Runtime.Py_Finalize();
+        }
     }
 }
diff --git a/src/embed_tests/TestTypeManager.cs b/src/embed_tests/TestTypeManager.cs
new file mode 100644
index 000000000..a4ef86913
--- /dev/null
+++ b/src/embed_tests/TestTypeManager.cs
@@ -0,0 +1,65 @@
+using NUnit.Framework;
+using Python.Runtime;
+using System.Runtime.InteropServices;
+
+namespace Python.EmbeddingTest
+{
+    class TestTypeManager
+    {
+        [SetUp]
+        public static void Init()
+        {
+            Runtime.Runtime.Initialize();
+        }
+
+        [TearDown]
+        public static void Fini()
+        {
+            // Don't shut down the runtime: if the python engine was initialized
+            // but not shut down by another test, we'd end up in a bad state.
+        }
+
+        [Test]
+        public static void TestNativeCode()
+        {
+            Assert.That(() => { var _ = TypeManager.NativeCode.Active; }, Throws.Nothing);
+            Assert.That(TypeManager.NativeCode.Active.Code.Length, Is.GreaterThan(0));
+        }
+
+        [Test]
+        public static void TestMemoryMapping()
+        {
+            Assert.That(() => { var _ = TypeManager.CreateMemoryMapper(); }, Throws.Nothing);
+            var mapper = TypeManager.CreateMemoryMapper();
+
+            // Allocate a read-write page.
+            int len = 12;
+            var page = mapper.MapWriteable(len);
+            Assert.That(() => { Marshal.WriteInt64(page, 17); }, Throws.Nothing);
+            Assert.That(Marshal.ReadInt64(page), Is.EqualTo(17));
+
+            // Mark it read-execute. We can still read, haven't changed any values.
+            mapper.SetReadExec(page, len);
+            Assert.That(Marshal.ReadInt64(page), Is.EqualTo(17));
+
+            // Test that we can't write to the protected page.
+            //
+            // We can't actually test access protection under Microsoft
+            // versions of .NET, because AccessViolationException is assumed to
+            // mean we're in a corrupted state:
+            //   https://stackoverflow.com/questions/3469368/how-to-handle-accessviolationexception
+            //
+            // We can test under Mono but it throws NRE instead of AccessViolationException.
+            //
+            // We can't use compiler flags because we compile with MONO_LINUX
+            // while running on the Microsoft .NET Core during continuous
+            // integration tests.
+            if (System.Type.GetType ("Mono.Runtime") != null)
+            {
+                // Mono throws NRE instead of AccessViolationException for some reason.
+                Assert.That(() => { Marshal.WriteInt64(page, 73); }, Throws.TypeOf<System.NullReferenceException>());
+                Assert.That(Marshal.ReadInt64(page), Is.EqualTo(17));
+            }
+        }
+    }
+}
diff --git a/src/embed_tests/dynamic.cs b/src/embed_tests/dynamic.cs
index 94397072a..81345cee7 100644
--- a/src/embed_tests/dynamic.cs
+++ b/src/embed_tests/dynamic.cs
@@ -12,13 +12,23 @@ public class DynamicTest
         [SetUp]
         public void SetUp()
         {
-            _gs = Py.GIL();
+            try {
+                _gs = Py.GIL();
+            } catch (Exception e) {
+                Console.WriteLine($"exception in SetUp: {e}");
+                throw;
+            }
         }
 
         [TearDown]
         public void Dispose()
         {
-            _gs.Dispose();
+            try {
+                _gs.Dispose();
+            } catch(Exception e) {
+                Console.WriteLine($"exception in TearDown: {e}");
+                throw;
+            }
         }
 
         /// <summary>
@@ -103,7 +113,7 @@ public void PassObjectInPython()
             Assert.AreEqual(sys.testattr3.ToString(), "True");
 
             // Compare in .NET
-            Assert.AreEqual(sys.testattr1, sys.testattr2);
+            Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));
         }
 
         /// <summary>
@@ -118,14 +128,15 @@ public void PassPyObjectInNet()
             sys.testattr2 = sys.testattr1;
 
             // Compare in Python
-            PyObject res = PythonEngine.RunString(
+            PythonEngine.RunSimpleString(
                 "import sys\n" +
                 "sys.testattr3 = sys.testattr1 is sys.testattr2\n"
             );
+
             Assert.AreEqual(sys.testattr3.ToString(), "True");
 
             // Compare in .NET
-            Assert.AreEqual(sys.testattr1, sys.testattr2);
+            Assert.IsTrue(sys.testattr1.Equals(sys.testattr2));
         }
     }
 }
diff --git a/src/embed_tests/packages.config b/src/embed_tests/packages.config
index 4cb01d3be..8c175f441 100644
--- a/src/embed_tests/packages.config
+++ b/src/embed_tests/packages.config
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="NUnit" version="3.6.0" targetFramework="net40" />
-  <package id="NUnit.ConsoleRunner" version="3.6.0" targetFramework="net40" />
+  <package id="NUnit" version="3.7.1" targetFramework="net40" />
+  <package id="NUnit.ConsoleRunner" version="3.7.0" targetFramework="net40" />
 </packages>
diff --git a/src/embed_tests/pyimport.cs b/src/embed_tests/pyimport.cs
index 3bb9a34d6..acb3433de 100644
--- a/src/embed_tests/pyimport.cs
+++ b/src/embed_tests/pyimport.cs
@@ -30,7 +30,11 @@ public void SetUp()
             /* Append the tests directory to sys.path
              * using reflection to circumvent the private
              * modifiers placed on most Runtime methods. */
+#if NETCOREAPP
+            const string s = "../../fixtures";
+#else
             const string s = "../fixtures";
+#endif
             string testPath = Path.Combine(TestContext.CurrentContext.TestDirectory, s);
 
             IntPtr str = Runtime.Runtime.PyString_FromString(testPath);
diff --git a/src/embed_tests/pyinitialize.cs b/src/embed_tests/pyinitialize.cs
index 2f9aae2c7..ea1d8d023 100644
--- a/src/embed_tests/pyinitialize.cs
+++ b/src/embed_tests/pyinitialize.cs
@@ -74,5 +74,65 @@ public void ReInitialize()
             }
             PythonEngine.Shutdown();
         }
+
+        [Test]
+        public void TestScopeIsShutdown()
+        {
+            PythonEngine.Initialize();
+            var scope = PyScopeManager.Global.Create("test");
+            PythonEngine.Shutdown();
+            Assert.That(PyScopeManager.Global.Contains("test"), Is.False);
+        }
+
+        /// <summary>
+        /// Helper for testing the shutdown handlers.
+        /// </summary>
+        int shutdown_count = 0;
+        void OnShutdownIncrement()
+        {
+            shutdown_count++;
+        }
+        void OnShutdownDouble()
+        {
+            shutdown_count *= 2;
+        }
+
+        /// <summary>
+        /// Test the shutdown handlers.
+        /// </summary>
+        [Test]
+        public void ShutdownHandlers()
+        {
+            // Test we can run one shutdown handler.
+            shutdown_count = 0;
+            PythonEngine.Initialize();
+            PythonEngine.AddShutdownHandler(OnShutdownIncrement);
+            PythonEngine.Shutdown();
+            Assert.That(shutdown_count, Is.EqualTo(1));
+
+            // Test we can run multiple shutdown handlers in the right order.
+            shutdown_count = 4;
+            PythonEngine.Initialize();
+            PythonEngine.AddShutdownHandler(OnShutdownIncrement);
+            PythonEngine.AddShutdownHandler(OnShutdownDouble);
+            PythonEngine.Shutdown();
+            // Correct: 4 * 2 + 1 = 9
+            // Wrong:  (4 + 1) * 2 = 10
+            Assert.That(shutdown_count, Is.EqualTo(9));
+
+            // Test we can remove shutdown handlers, handling duplicates.
+            shutdown_count = 4;
+            PythonEngine.Initialize();
+            PythonEngine.AddShutdownHandler(OnShutdownIncrement);
+            PythonEngine.AddShutdownHandler(OnShutdownIncrement);
+            PythonEngine.AddShutdownHandler(OnShutdownDouble);
+            PythonEngine.AddShutdownHandler(OnShutdownIncrement);
+            PythonEngine.AddShutdownHandler(OnShutdownDouble);
+            PythonEngine.RemoveShutdownHandler(OnShutdownDouble);
+            PythonEngine.Shutdown();
+            // Correct: (4 + 1) * 2 + 1 + 1 = 12
+            // Wrong:   (4 * 2) + 1 + 1 + 1 = 11
+            Assert.That(shutdown_count, Is.EqualTo(12));
+        }
     }
 }
diff --git a/src/embed_tests/pyrunstring.cs b/src/embed_tests/pyrunstring.cs
index 81a1b07ca..07875a2a8 100644
--- a/src/embed_tests/pyrunstring.cs
+++ b/src/embed_tests/pyrunstring.cs
@@ -57,5 +57,20 @@ public void TestExec()
             object c = locals.GetItem("c").AsManagedObject(typeof(int));
             Assert.AreEqual(111, c);
         }
+
+        [Test]
+        public void TestExec2()
+        {
+            string code = @"
+class Test1():
+   pass
+
+class Test2():
+   def __init__(self):
+       Test1()
+
+Test2()";
+            PythonEngine.Exec(code);
+        }
     }
 }
diff --git a/src/runtime/CustomMarshaler.cs b/src/runtime/CustomMarshaler.cs
index 90bb77a71..b51911816 100644
--- a/src/runtime/CustomMarshaler.cs
+++ b/src/runtime/CustomMarshaler.cs
@@ -91,13 +91,13 @@ public static int GetUnicodeByteLength(IntPtr p)
             var len = 0;
             while (true)
             {
-                int c = Runtime.UCS == 2
+                int c = Runtime._UCS == 2
                     ? Marshal.ReadInt16(p, len * 2)
                     : Marshal.ReadInt32(p, len * 4);
 
                 if (c == 0)
                 {
-                    return len * Runtime.UCS;
+                    return len * Runtime._UCS;
                 }
                 checked
                 {
@@ -163,7 +163,7 @@ public override IntPtr MarshalManagedToNative(object managedObj)
             }
 
             int totalStrLength = argv.Sum(arg => arg.Length + 1);
-            int memSize = argv.Length * IntPtr.Size + totalStrLength * Runtime.UCS;
+            int memSize = argv.Length * IntPtr.Size + totalStrLength * Runtime._UCS;
 
             IntPtr mem = Marshal.AllocHGlobal(memSize);
             try
diff --git a/src/runtime/Python.Runtime.15.csproj b/src/runtime/Python.Runtime.15.csproj
new file mode 100644
index 000000000..794645994
--- /dev/null
+++ b/src/runtime/Python.Runtime.15.csproj
@@ -0,0 +1,140 @@
+<Project>
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+  <PropertyGroup>
+    <TargetFrameworks>net40;netstandard2.0</TargetFrameworks>
+    <Platforms>AnyCPU</Platforms>
+    <Configurations>DebugMono;DebugMonoPY3;ReleaseMono;ReleaseMonoPY3;DebugWin;DebugWinPY3;ReleaseWin;ReleaseWinPY3</Configurations>
+    <AssetTargetFallback Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono'))">net45</AssetTargetFallback>
+    <RootNamespace>Python.Runtime</RootNamespace>
+    <AssemblyName>Python.Runtime</AssemblyName>
+    <PackageId>Python.Runtime</PackageId>
+    <VersionPrefix>2.4.0</VersionPrefix>
+    <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
+    <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
+    <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
+    <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
+    <GenerateAssemblyDescriptionAttribute>false</GenerateAssemblyDescriptionAttribute>
+    <OutputPath>bin\</OutputPath>
+    <AppendTargetFrameworkToOutputPath Condition="'$(TargetFramework)'=='net40'">false</AppendTargetFrameworkToOutputPath>
+    <DocumentationFile Condition="'$(TargetFramework)'=='net40'">$(OutputPath)\$(AssemblyName).xml</DocumentationFile>
+    <DocumentationFile Condition="'$(TargetFramework)'!='net40'">$(OutputPath)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
+    <NoWarn>1591;NU1701</NoWarn>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <PythonBuildDir Condition="'$(PythonBuildDir)' == ''">$(SolutionDir)\bin\</PythonBuildDir>
+    <PublishDir Condition="'$(TargetFramework)'!='net40'">$(PythonBuildDir)\$(TargetFramework)\</PublishDir>
+    <LangVersion>6</LangVersion>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+    <AssemblyOriginatorKeyFile>..\pythonnet.snk</AssemblyOriginatorKeyFile>
+    <CustomDefineConstants Condition="'$(CustomDefineConstants)' == ''">$(PYTHONNET_DEFINE_CONSTANTS)</CustomDefineConstants>
+    <BaseDefineConstants>XPLAT</BaseDefineConstants>
+    <DefineConstants>$(DefineConstants);$(CustomDefineConstants);$(BaseDefineConstants);</DefineConstants>
+    <DefineConstants Condition="'$(TargetFramework)'=='netstandard2.0'">$(DefineConstants);NETSTANDARD</DefineConstants>
+    <DefineConstants Condition="'$(BuildingInsideVisualStudio)' == 'true' AND '$(CustomDefineConstants)' != '' AND $(Configuration.Contains('Debug'))">$(DefineConstants);TRACE;DEBUG</DefineConstants>
+    <FrameworkPathOverride Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono'))">$(NuGetPackageRoot)\microsoft.targetingpack.netframework.v4.5\1.0.1\lib\net45\</FrameworkPathOverride>
+    <Python2Version>$(PYTHONNET_PY2_VERSION)</Python2Version>
+    <Python2Version Condition="'$(Python2Version)'==''">PYTHON27</Python2Version>
+    <Python3Version>$(PYTHONNET_PY3_VERSION)</Python3Version>
+    <Python3Version Condition="'$(Python3Version)'==''">PYTHON37</Python3Version>
+    <PythonWinDefineConstants>$(PYTHONNET_WIN_DEFINE_CONSTANTS)</PythonWinDefineConstants>
+    <PythonWinDefineConstants Condition="'$(PythonWinDefineConstants)'==''">UCS2</PythonWinDefineConstants>
+    <PythonMonoDefineConstants>$(PYTHONNET_MONO_DEFINE_CONSTANTS)</PythonMonoDefineConstants>
+    <PythonMonoDefineConstants Condition="'$(PythonMonoDefineConstants)'==''">UCS4;MONO_LINUX;PYTHON_WITH_PYMALLOC</PythonMonoDefineConstants>
+    <PythonInteropFile Condition="'$(PythonInteropFile)'==''">$(PYTHONNET_INTEROP_FILE)</PythonInteropFile>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>true</Optimize>
+    <DebugType>portable</DebugType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMono'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;$(Python2Version);$(PythonMonoDefineConstants)</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMonoPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;$(Python3Version);$(PythonMonoDefineConstants)</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugMono'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;$(Python2Version);$(PythonMonoDefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugMonoPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;$(Python3Version);$(PythonMonoDefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWin'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;$(Python2Version);$(PythonWinDefineConstants)</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWinPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;$(Python3Version);$(PythonWinDefineConstants)</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugWin'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON2;$(Python2Version);$(PythonWinDefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'DebugWinPY3'">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);PYTHON3;$(Python3Version);$(PythonWinDefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+
+  <ItemGroup Condition=" '$(PythonInteropFile)' != '' ">
+    <Compile Remove="interop*.cs" />
+    <Compile Include="interop.cs" />
+    <Compile Include="$(PythonInteropFile)" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Include="..\pythonnet.snk" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Remove="resources\clr.py" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Include="..\SharedAssemblyInfo.cs" Link="Properties\SharedAssemblyInfo.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="resources\clr.py">
+      <LogicalName>clr.py</LogicalName>
+    </EmbeddedResource>
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="System.Security.Permissions" Version="4.4.0" />
+    <PackageReference Include="System.Reflection.Emit" Version="4.3.0" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <Reference Include="Microsoft.CSharp" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)'=='net40'">
+    <PackageReference Include="Microsoft.TargetingPack.NETFramework.v4.5" Version="1.0.1" ExcludeAssets="All" PrivateAssets="All" />
+  </ItemGroup>
+
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetAssembly>$(TargetPath)</TargetAssembly>
+    <TargetAssemblyPdb>$(TargetDir)$(TargetName).pdb</TargetAssemblyPdb>
+  </PropertyGroup>
+
+  <Target Name="BeforeBuild" Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono')) AND '$(OS)' != 'Windows_NT'">
+    <!--Endless war!-->
+    <Exec Command="[[ -e $(NuGetPackageRoot)/microsoft.targetingpack.netframework.v4.5/1.0.1/lib/net45/System.Xml.dll ]] || cp $(NuGetPackageRoot)/microsoft.targetingpack.netframework.v4.5/1.0.1/lib/net45/System.XML.dll $(NuGetPackageRoot)/microsoft.targetingpack.netframework.v4.5/1.0.1/lib/net45/System.Xml.dll" />
+  </Target>
+  <Target Name="AfterBuild">
+    <Copy Condition="'$(TargetFramework)'=='net40'" SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
+  </Target>
+</Project>
diff --git a/src/runtime/Python.Runtime.csproj b/src/runtime/Python.Runtime.csproj
index 8580b7f61..fc155ca91 100644
--- a/src/runtime/Python.Runtime.csproj
+++ b/src/runtime/Python.Runtime.csproj
@@ -20,19 +20,21 @@
     <SignAssembly>false</SignAssembly>
     <AssemblyOriginatorKeyFile>..\pythonnet.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
-  <PropertyGroup Condition=" '$(Platform)' == 'x86'">
+  <!--We can relax binding to platform because code references no any platform dependent assemblies-->
+  <!--This will allows to use any build of this assebly as a compile ref assebly-->
+  <!--<PropertyGroup Condition=" '$(Platform)' == 'x86'">
     <PlatformTarget>x86</PlatformTarget>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Platform)' == 'x64'">
     <PlatformTarget>x64</PlatformTarget>
-  </PropertyGroup>
+  </PropertyGroup>-->
   <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMono'">
     <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON2;PYTHON27;UCS4</DefineConstants>
     <Optimize>true</Optimize>
     <DebugType>pdbonly</DebugType>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseMonoPY3'">
-    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON36;UCS4</DefineConstants>
+    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4</DefineConstants>
     <Optimize>true</Optimize>
     <DebugType>pdbonly</DebugType>
   </PropertyGroup>
@@ -44,7 +46,7 @@
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'DebugMonoPY3'">
     <DebugSymbols>true</DebugSymbols>
-    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON36;UCS4;TRACE;DEBUG</DefineConstants>
+    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS4;TRACE;DEBUG</DefineConstants>
     <Optimize>false</Optimize>
     <DebugType>full</DebugType>
   </PropertyGroup>
@@ -54,7 +56,7 @@
     <DebugType>pdbonly</DebugType>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'ReleaseWinPY3'">
-    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON36;UCS2</DefineConstants>
+    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2</DefineConstants>
     <Optimize>true</Optimize>
     <DebugType>pdbonly</DebugType>
   </PropertyGroup>
@@ -66,7 +68,7 @@
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'DebugWinPY3'">
     <DebugSymbols>true</DebugSymbols>
-    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON36;UCS2;TRACE;DEBUG</DefineConstants>
+    <DefineConstants Condition="'$(DefineConstants)' == ''">PYTHON3;PYTHON37;UCS2;TRACE;DEBUG</DefineConstants>
     <Optimize>false</Optimize>
     <DebugType>full</DebugType>
   </PropertyGroup>
@@ -127,6 +129,7 @@
     <Compile Include="pylong.cs" />
     <Compile Include="pynumber.cs" />
     <Compile Include="pyobject.cs" />
+    <Compile Include="pyscope.cs" />
     <Compile Include="pysequence.cs" />
     <Compile Include="pystring.cs" />
     <Compile Include="pythonengine.cs" />
@@ -135,16 +138,17 @@
     <Compile Include="runtime.cs" />
     <Compile Include="typemanager.cs" />
     <Compile Include="typemethod.cs" />
+    <Compile Include="Util.cs" />
   </ItemGroup>
   <ItemGroup Condition=" '$(PythonInteropFile)' != '' ">
     <Compile Include="$(PythonInteropFile)" />
   </ItemGroup>
   <ItemGroup Condition=" '$(PythonInteropFile)' == '' ">
     <Compile Include="interop27.cs" />
-    <Compile Include="interop33.cs" />
     <Compile Include="interop34.cs" />
     <Compile Include="interop35.cs" />
     <Compile Include="interop36.cs" />
+    <Compile Include="interop37.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="..\pythonnet.snk" />
@@ -161,6 +165,6 @@
   </PropertyGroup>
   <Target Name="AfterBuild">
     <Copy SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
-    <Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
   </Target>
 </Project>
diff --git a/src/runtime/Util.cs b/src/runtime/Util.cs
new file mode 100644
index 000000000..dc5f78608
--- /dev/null
+++ b/src/runtime/Util.cs
@@ -0,0 +1,33 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Python.Runtime
+{
+    internal class Util
+    {
+        internal static Int64 ReadCLong(IntPtr tp, int offset)
+        {
+            // On Windows, a C long is always 32 bits.
+            if (Runtime.IsWindows || Runtime.Is32Bit)
+            {
+                return Marshal.ReadInt32(tp, offset);
+            }
+            else
+            {
+                return Marshal.ReadInt64(tp, offset);
+            }
+        }
+
+        internal static void WriteCLong(IntPtr type, int offset, Int64 flags)
+        {
+            if (Runtime.IsWindows || Runtime.Is32Bit)
+            {
+                Marshal.WriteInt32(type, offset, (Int32)(flags & 0xffffffffL));
+            }
+            else
+            {
+                Marshal.WriteInt64(type, offset, flags);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/runtime/arrayobject.cs b/src/runtime/arrayobject.cs
index a10688749..c37295704 100644
--- a/src/runtime/arrayobject.cs
+++ b/src/runtime/arrayobject.cs
@@ -93,7 +93,7 @@ public static IntPtr mp_subscript(IntPtr ob, IntPtr idx)
                 return IntPtr.Zero;
             }
 
-            int count = Runtime.PyTuple_Size(idx);
+            var count = Runtime.PyTuple_Size(idx);
 
             var args = new int[count];
 
@@ -186,7 +186,7 @@ public static int mp_ass_subscript(IntPtr ob, IntPtr idx, IntPtr v)
                 return -1;
             }
 
-            int count = Runtime.PyTuple_Size(idx);
+            var count = Runtime.PyTuple_Size(idx);
             var args = new int[count];
 
             for (var i = 0; i < count; i++)
diff --git a/src/runtime/assemblymanager.cs b/src/runtime/assemblymanager.cs
index 06a4449a2..3085bb639 100644
--- a/src/runtime/assemblymanager.cs
+++ b/src/runtime/assemblymanager.cs
@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using System.Reflection;
 using System.Threading;
 
@@ -17,16 +18,24 @@ internal class AssemblyManager
     {
         // modified from event handlers below, potentially triggered from different .NET threads
         // therefore this should be a ConcurrentDictionary
-        private static ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>> namespaces;
+        //
+        // WARNING: Dangerous if cross-app domain usage is ever supported
+        //    Reusing the dictionary with assemblies accross multiple initializations is problematic. 
+        //    Loading happens from CurrentDomain (see line 53). And if the first call is from AppDomain that is later unloaded, 
+        //    than it can end up referring to assemblies that are already unloaded (default behavior after unload appDomain - 
+        //     unless LoaderOptimization.MultiDomain is used);
+        //    So for multidomain support it is better to have the dict. recreated for each app-domain initialization
+        private static ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>> namespaces =
+            new ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>>();
         //private static Dictionary<string, Dictionary<string, string>> generics;
         private static AssemblyLoadEventHandler lhandler;
         private static ResolveEventHandler rhandler;
 
         // updated only under GIL?
-        private static Dictionary<string, int> probed;
+        private static Dictionary<string, int> probed = new Dictionary<string, int>(32);
 
         // modified from event handlers below, potentially triggered from different .NET threads
-        private static AssemblyList assemblies;
+        private static ConcurrentQueue<Assembly> assemblies;
         internal static List<string> pypath;
 
         private AssemblyManager()
@@ -40,10 +49,7 @@ private AssemblyManager()
         /// </summary>
         internal static void Initialize()
         {
-            namespaces = new ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>>();
-            probed = new Dictionary<string, int>(32);
-            //generics = new Dictionary<string, Dictionary<string, string>>();
-            assemblies = new AssemblyList(16);
+            assemblies = new ConcurrentQueue<Assembly>();
             pypath = new List<string>(16);
 
             AppDomain domain = AppDomain.CurrentDomain;
@@ -60,7 +66,7 @@ internal static void Initialize()
                 try
                 {
                     ScanAssembly(a);
-                    assemblies.Add(a);
+                    assemblies.Enqueue(a);
                 }
                 catch (Exception ex)
                 {
@@ -91,7 +97,7 @@ internal static void Shutdown()
         private static void AssemblyLoadHandler(object ob, AssemblyLoadEventArgs args)
         {
             Assembly assembly = args.LoadedAssembly;
-            assemblies.Add(assembly);
+            assemblies.Enqueue(assembly);
             ScanAssembly(assembly);
         }
 
@@ -132,7 +138,7 @@ private static Assembly ResolveHandler(object ob, ResolveEventArgs args)
         internal static void UpdatePath()
         {
             IntPtr list = Runtime.PySys_GetObject("path");
-            int count = Runtime.PyList_Size(list);
+            var count = Runtime.PyList_Size(list);
             if (count != pypath.Count)
             {
                 pypath.Clear();
@@ -343,9 +349,7 @@ internal static void ScanAssembly(Assembly assembly)
             // A couple of things we want to do here: first, we want to
             // gather a list of all of the namespaces contributed to by
             // the assembly.
-
-            Type[] types = assembly.GetTypes();
-            foreach (Type t in types)
+            foreach (Type t in GetTypes(assembly))
             {
                 string ns = t.Namespace ?? "";
                 if (!namespaces.ContainsKey(ns))
@@ -419,10 +423,9 @@ public static List<string> GetNames(string nsname)
             {
                 foreach (Assembly a in namespaces[nsname].Keys)
                 {
-                    Type[] types = a.GetTypes();
-                    foreach (Type t in types)
+                    foreach (Type t in GetTypes(a))
                     {
-                        if ((t.Namespace ?? "") == nsname)
+                        if ((t.Namespace ?? "") == nsname && !t.IsNested)
                         {
                             names.Add(t.Name);
                         }
@@ -462,102 +465,31 @@ public static Type LookupType(string qname)
             return null;
         }
 
-        /// <summary>
-        /// Wrapper around List&lt;Assembly&gt; for thread safe access
-        /// </summary>
-        private class AssemblyList : IEnumerable<Assembly>
+        internal static Type[] GetTypes(Assembly a)
         {
-            private readonly List<Assembly> _list;
-            private readonly ReaderWriterLockSlim _lock;
-
-            public AssemblyList(int capacity)
-            {
-                _list = new List<Assembly>(capacity);
-                _lock = new ReaderWriterLockSlim();
-            }
-
-            public int Count
-            {
-                get
-                {
-                    _lock.EnterReadLock();
-                    try
-                    {
-                        return _list.Count;
-                    }
-                    finally
-                    {
-                        _lock.ExitReadLock();
-                    }
-                }
-            }
-
-            public void Add(Assembly assembly)
+            if (a.IsDynamic)
             {
-                _lock.EnterWriteLock();
                 try
                 {
-                    _list.Add(assembly);
+                    return a.GetTypes();
                 }
-                finally
+                catch (ReflectionTypeLoadException exc)
                 {
-                    _lock.ExitWriteLock();
+                    // Return all types that were successfully loaded
+                    return exc.Types.Where(x => x != null).ToArray();
                 }
             }
-
-            public IEnumerator GetEnumerator()
-            {
-                return ((IEnumerable<Assembly>)this).GetEnumerator();
-            }
-
-            /// <summary>
-            /// Enumerator wrapping around <see cref="AssemblyList._list" />'s enumerator.
-            /// Acquires and releases a read lock on <see cref="AssemblyList._lock" /> during enumeration
-            /// </summary>
-            private class Enumerator : IEnumerator<Assembly>
+            else
             {
-                private readonly AssemblyList _assemblyList;
-
-                private readonly IEnumerator<Assembly> _listEnumerator;
-
-                public Enumerator(AssemblyList assemblyList)
-                {
-                    _assemblyList = assemblyList;
-                    _assemblyList._lock.EnterReadLock();
-                    _listEnumerator = _assemblyList._list.GetEnumerator();
-                }
-
-                public void Dispose()
-                {
-                    _listEnumerator.Dispose();
-                    _assemblyList._lock.ExitReadLock();
-                }
-
-                public bool MoveNext()
-                {
-                    return _listEnumerator.MoveNext();
-                }
-
-                public void Reset()
-                {
-                    _listEnumerator.Reset();
-                }
-
-                public Assembly Current
+                try
                 {
-                    get { return _listEnumerator.Current; }
+                    return a.GetExportedTypes();
                 }
-
-                object IEnumerator.Current
+                catch (FileNotFoundException)
                 {
-                    get { return Current; }
+                    return new Type[0];
                 }
             }
-
-            IEnumerator<Assembly> IEnumerable<Assembly>.GetEnumerator()
-            {
-                return new Enumerator(this);
-            }
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/runtime/classbase.cs b/src/runtime/classbase.cs
index 4dd3b5364..5846fa82a 100644
--- a/src/runtime/classbase.cs
+++ b/src/runtime/classbase.cs
@@ -247,24 +247,6 @@ public static IntPtr tp_str(IntPtr ob)
         }
 
 
-        /// <summary>
-        /// Default implementations for required Python GC support.
-        /// </summary>
-        public static int tp_traverse(IntPtr ob, IntPtr func, IntPtr args)
-        {
-            return 0;
-        }
-
-        public static int tp_clear(IntPtr ob)
-        {
-            return 0;
-        }
-
-        public static int tp_is_gc(IntPtr type)
-        {
-            return 1;
-        }
-
         /// <summary>
         /// Standard dealloc implementation for instances of reflected types.
         /// </summary>
diff --git a/src/runtime/classderived.cs b/src/runtime/classderived.cs
index c180f9acc..ec3734ea5 100644
--- a/src/runtime/classderived.cs
+++ b/src/runtime/classderived.cs
@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Emit;
+using System.Resources;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 
@@ -32,6 +33,12 @@ static ClassDerivedObject()
             moduleBuilders = new Dictionary<Tuple<string, string>, ModuleBuilder>();
         }
 
+        public static void Reset()
+        {
+            assemblyBuilders = new Dictionary<string, AssemblyBuilder>();
+            moduleBuilders = new Dictionary<Tuple<string, string>, ModuleBuilder>();
+        }
+
         internal ClassDerivedObject(Type tp) : base(tp)
         {
         }
@@ -808,7 +815,6 @@ public static void InvokeCtor(IPythonDerivedType obj, string origCtorName, objec
                 obj,
                 args);
 
-            var disposeList = new List<PyObject>();
             CLRObject self = null;
             IntPtr gs = Runtime.PyGILState_Ensure();
             try
@@ -821,42 +827,9 @@ public static void InvokeCtor(IPythonDerivedType obj, string origCtorName, objec
                 // object to be collected.
                 FieldInfo fi = obj.GetType().GetField("__pyobj__");
                 fi.SetValue(obj, self);
-
-                Runtime.XIncref(self.pyHandle);
-                var pyself = new PyObject(self.pyHandle);
-                disposeList.Add(pyself);
-
-                Runtime.XIncref(Runtime.PyNone);
-                var pynone = new PyObject(Runtime.PyNone);
-                disposeList.Add(pynone);
-
-                // call __init__
-                PyObject init = pyself.GetAttr("__init__", pynone);
-                disposeList.Add(init);
-                if (init.Handle != Runtime.PyNone)
-                {
-                    // if __init__ hasn't been overridden then it will be a managed object
-                    ManagedType managedMethod = ManagedType.GetManagedObject(init.Handle);
-                    if (null == managedMethod)
-                    {
-                        var pyargs = new PyObject[args.Length];
-                        for (var i = 0; i < args.Length; ++i)
-                        {
-                            pyargs[i] = new PyObject(Converter.ToPython(args[i], args[i]?.GetType()));
-                            disposeList.Add(pyargs[i]);
-                        }
-
-                        disposeList.Add(init.Invoke(pyargs));
-                    }
-                }
             }
             finally
             {
-                foreach (PyObject x in disposeList)
-                {
-                    x?.Dispose();
-                }
-
                 // Decrement the python object's reference count.
                 // This doesn't actually destroy the object, it just sets the reference to this object
                 // to be a weak reference and it will be destroyed when the C# object is destroyed.
diff --git a/src/runtime/classmanager.cs b/src/runtime/classmanager.cs
index 6a9d40ebd..0b084a49d 100644
--- a/src/runtime/classmanager.cs
+++ b/src/runtime/classmanager.cs
@@ -34,6 +34,11 @@ static ClassManager()
             dtype = typeof(MulticastDelegate);
         }
 
+        public static void Reset()
+        {
+            cache = new Dictionary<Type, ClassBase>(128);
+        }
+
         /// <summary>
         /// Return the ClassBase-derived instance that implements a particular
         /// reflected managed type, creating it if it doesn't yet exist.
diff --git a/src/runtime/classobject.cs b/src/runtime/classobject.cs
index 46257c73f..83d761fd0 100644
--- a/src/runtime/classobject.cs
+++ b/src/runtime/classobject.cs
@@ -230,10 +230,10 @@ public static int mp_ass_subscript(IntPtr ob, IntPtr idx, IntPtr v)
             }
 
             // Get the args passed in.
-            int i = Runtime.PyTuple_Size(args);
+            var i = Runtime.PyTuple_Size(args);
             IntPtr defaultArgs = cls.indexer.GetDefaultArgs(args);
-            int numOfDefaultArgs = Runtime.PyTuple_Size(defaultArgs);
-            int temp = i + numOfDefaultArgs;
+            var numOfDefaultArgs = Runtime.PyTuple_Size(defaultArgs);
+            var temp = i + numOfDefaultArgs;
             IntPtr real = Runtime.PyTuple_New(temp + 1);
             for (var n = 0; n < i; n++)
             {
diff --git a/src/runtime/clrobject.cs b/src/runtime/clrobject.cs
index 472e5dcbb..502677655 100644
--- a/src/runtime/clrobject.cs
+++ b/src/runtime/clrobject.cs
@@ -11,7 +11,7 @@ internal CLRObject(object ob, IntPtr tp)
         {
             IntPtr py = Runtime.PyType_GenericAlloc(tp, 0);
 
-            var flags = (int)Marshal.ReadIntPtr(tp, TypeOffset.tp_flags);
+            long flags = Util.ReadCLong(tp, TypeOffset.tp_flags);
             if ((flags & TypeFlags.Subclass) != 0)
             {
                 IntPtr dict = Marshal.ReadIntPtr(py, ObjectOffset.DictOffset(tp));
diff --git a/src/runtime/constructorbinding.cs b/src/runtime/constructorbinding.cs
index 4839f9913..3908628b9 100644
--- a/src/runtime/constructorbinding.cs
+++ b/src/runtime/constructorbinding.cs
@@ -75,7 +75,7 @@ public static IntPtr tp_descr_get(IntPtr op, IntPtr instance, IntPtr owner)
                     return Exceptions.RaiseTypeError("How in the world could that happen!");
                 }
             }*/
-            Runtime.XIncref(self.pyHandle); // Decref'd by the interpreter.
+            Runtime.XIncref(self.pyHandle);
             return self.pyHandle;
         }
 
@@ -105,8 +105,6 @@ public static IntPtr mp_subscript(IntPtr op, IntPtr key)
             }
             var boundCtor = new BoundContructor(self.type, self.pyTypeHndl, self.ctorBinder, ci);
 
-            /* Since nothing is cached, do we need the increment???
-            Runtime.XIncref(boundCtor.pyHandle);  // Decref'd by the interpreter??? */
             return boundCtor.pyHandle;
         }
 
diff --git a/src/runtime/converter.cs b/src/runtime/converter.cs
index b66150a29..11c67bf82 100644
--- a/src/runtime/converter.cs
+++ b/src/runtime/converter.cs
@@ -1,9 +1,11 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Security;
+using System.ComponentModel;
 
 namespace Python.Runtime
 {
@@ -133,12 +135,36 @@ internal static IntPtr ToPython(object value, Type type)
                 return result;
             }
 
+			if (value is IList && !(value is INotifyPropertyChanged) && value.GetType().IsGenericType)
+			{
+                using (var resultlist = new PyList())
+                {
+                    foreach (object o in (IEnumerable)value)
+                    {
+                        using (var p = new PyObject(ToPython(o, o?.GetType())))
+                        {
+                            resultlist.Append(p);
+                        }
+                    }
+                    Runtime.XIncref(resultlist.Handle);
+                    return resultlist.Handle;
+                }
+            }
+
             // it the type is a python subclass of a managed type then return the
             // underlying python object rather than construct a new wrapper object.
             var pyderived = value as IPythonDerivedType;
             if (null != pyderived)
             {
+                #if NETSTANDARD
                 return ClassDerivedObject.ToPython(pyderived);
+                #else
+                // if object is remote don't do this
+                if (!System.Runtime.Remoting.RemotingServices.IsTransparentProxy(pyderived))
+                {
+                    return ClassDerivedObject.ToPython(pyderived);
+                }
+                #endif
             }
 
             // hmm - from Python, we almost never care what the declared
@@ -301,6 +327,17 @@ internal static bool ToManagedValue(IntPtr value, Type obType,
                 return true;
             }
 
+            if (obType.IsGenericType && obType.GetGenericTypeDefinition() == typeof(Nullable<>))
+            {
+                if( value == Runtime.PyNone )
+                {
+                    result = null;
+                    return true;
+                }
+                // Set type to underlying type
+                obType = obType.GetGenericArguments()[0];
+            }
+
             if (obType.IsArray)
             {
                 return ToArray(value, obType, out result, setError);
@@ -742,10 +779,14 @@ private static bool ToPrimitive(IntPtr value, Type obType, out object result, bo
                         goto type_error;
                     }
                     double dd = Runtime.PyFloat_AsDouble(op);
+                    Runtime.CheckExceptionOccurred();
                     Runtime.XDecref(op);
                     if (dd > Single.MaxValue || dd < Single.MinValue)
                     {
-                        goto overflow;
+                        if (!double.IsInfinity(dd))
+                        {
+                            goto overflow;
+                        }
                     }
                     result = (float)dd;
                     return true;
@@ -757,11 +798,8 @@ private static bool ToPrimitive(IntPtr value, Type obType, out object result, bo
                         goto type_error;
                     }
                     double d = Runtime.PyFloat_AsDouble(op);
+                    Runtime.CheckExceptionOccurred();
                     Runtime.XDecref(op);
-                    if (d > Double.MaxValue || d < Double.MinValue)
-                    {
-                        goto overflow;
-                    }
                     result = d;
                     return true;
             }
@@ -805,7 +843,7 @@ private static void SetConversionError(IntPtr value, Type target)
         private static bool ToArray(IntPtr value, Type obType, out object result, bool setError)
         {
             Type elementType = obType.GetElementType();
-            int size = Runtime.PySequence_Size(value);
+            var size = Runtime.PySequence_Size(value);
             result = null;
 
             if (size < 0)
diff --git a/src/runtime/debughelper.cs b/src/runtime/debughelper.cs
index 2a91a74b4..3fe9ee5bb 100644
--- a/src/runtime/debughelper.cs
+++ b/src/runtime/debughelper.cs
@@ -116,10 +116,10 @@ internal static void debug(string msg)
             Console.WriteLine("  {0}", msg);
         }
 
-        /// <summary>
+        /// <summary>
         /// Helper function to inspect/compare managed to native conversions.
-        /// Especially useful when debugging CustomMarshaler.
-        /// </summary>
+        /// Especially useful when debugging CustomMarshaler.
+        /// </summary>
         /// <param name="bytes"></param>
         [Conditional("DEBUG")]
         public static void PrintHexBytes(byte[] bytes)
diff --git a/src/runtime/delegatemanager.cs b/src/runtime/delegatemanager.cs
index df5eec427..7632816d1 100644
--- a/src/runtime/delegatemanager.cs
+++ b/src/runtime/delegatemanager.cs
@@ -195,6 +195,10 @@ public Dispatcher(IntPtr target, Type dtype)
 
         ~Dispatcher()
         {
+            // We needs to disable Finalizers until it's valid implementation.
+            // Current implementation can produce low probability floating bugs.
+            return;
+
             // Note: the managed GC thread can run and try to free one of
             // these *after* the Python runtime has been finalized!
             if (Runtime.Py_IsInitialized() > 0)
diff --git a/src/runtime/exceptions.cs b/src/runtime/exceptions.cs
index 9023cfcfa..8bed0abfd 100644
--- a/src/runtime/exceptions.cs
+++ b/src/runtime/exceptions.cs
@@ -256,7 +256,10 @@ public static void SetError(Exception e)
             var pe = e as PythonException;
             if (pe != null)
             {
-                Runtime.PyErr_SetObject(pe.PyType, pe.PyValue);
+                Runtime.XIncref(pe.PyType);
+                Runtime.XIncref(pe.PyValue);
+                Runtime.XIncref(pe.PyTB);
+                Runtime.PyErr_Restore(pe.PyType, pe.PyValue, pe.PyTB);
                 return;
             }
 
@@ -276,7 +279,7 @@ public static void SetError(Exception e)
         /// </remarks>
         public static bool ErrorOccurred()
         {
-            return Runtime.PyErr_Occurred() != 0;
+            return Runtime.PyErr_Occurred() != IntPtr.Zero;
         }
 
         /// <summary>
diff --git a/src/runtime/extensiontype.cs b/src/runtime/extensiontype.cs
index 9569b0485..693a46f42 100644
--- a/src/runtime/extensiontype.cs
+++ b/src/runtime/extensiontype.cs
@@ -81,27 +81,6 @@ public static int tp_descr_set(IntPtr ds, IntPtr ob, IntPtr val)
         }
 
 
-        /// <summary>
-        /// Required Python GC support.
-        /// </summary>
-        public static int tp_traverse(IntPtr ob, IntPtr func, IntPtr args)
-        {
-            return 0;
-        }
-
-
-        public static int tp_clear(IntPtr ob)
-        {
-            return 0;
-        }
-
-
-        public static int tp_is_gc(IntPtr type)
-        {
-            return 1;
-        }
-
-
         /// <summary>
         /// Default dealloc implementation.
         /// </summary>
diff --git a/src/runtime/genericutil.cs b/src/runtime/genericutil.cs
index 9772d082f..3a230e12c 100644
--- a/src/runtime/genericutil.cs
+++ b/src/runtime/genericutil.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Resources;
 
 namespace Python.Runtime
 {
@@ -20,6 +21,11 @@ static GenericUtil()
             mapping = new Dictionary<string, Dictionary<string, List<string>>>();
         }
 
+        public static void Reset()
+        {
+            mapping = new Dictionary<string, Dictionary<string, List<string>>>();
+        }
+
         /// <summary>
         /// Register a generic type that appears in a given namespace.
         /// </summary>
diff --git a/src/runtime/importhook.cs b/src/runtime/importhook.cs
index bc9ac5eee..7e4a208f5 100644
--- a/src/runtime/importhook.cs
+++ b/src/runtime/importhook.cs
@@ -155,7 +155,7 @@ public static IntPtr __import__(IntPtr self, IntPtr args, IntPtr kw)
             // hook is saved as this.py_import. This version handles CLR
             // import and defers to the normal builtin for everything else.
 
-            int num_args = Runtime.PyTuple_Size(args);
+            var num_args = Runtime.PyTuple_Size(args);
             if (num_args < 1)
             {
                 return Exceptions.RaiseTypeError("__import__() takes at least 1 argument (0 given)");
@@ -237,6 +237,11 @@ public static IntPtr __import__(IntPtr self, IntPtr args, IntPtr kw)
                 if (res != IntPtr.Zero)
                 {
                     // There was no error.
+                    if (fromlist && IsLoadAll(fromList))
+                    {
+                        var mod = ManagedType.GetManagedObject(res) as ModuleObject;
+                        mod?.LoadNames();
+                    }
                     return res;
                 }
                 // There was an error
@@ -290,6 +295,11 @@ public static IntPtr __import__(IntPtr self, IntPtr args, IntPtr kw)
             {
                 if (fromlist)
                 {
+                    if (IsLoadAll(fromList))
+                    {
+                        var mod = ManagedType.GetManagedObject(module) as ModuleObject;
+                        mod?.LoadNames();
+                    }
                     Runtime.XIncref(module);
                     return module;
                 }
@@ -345,20 +355,33 @@ public static IntPtr __import__(IntPtr self, IntPtr args, IntPtr kw)
                 }
             }
 
-            ModuleObject mod = fromlist ? tail : head;
-
-            if (fromlist && Runtime.PySequence_Size(fromList) == 1)
             {
-                IntPtr fp = Runtime.PySequence_GetItem(fromList, 0);
-                if (!CLRModule.preload && Runtime.GetManagedString(fp) == "*")
+                var mod = fromlist ? tail : head;
+
+                if (fromlist && IsLoadAll(fromList))
                 {
                     mod.LoadNames();
                 }
-                Runtime.XDecref(fp);
+
+                Runtime.XIncref(mod.pyHandle);
+                return mod.pyHandle;
             }
+        }
 
-            Runtime.XIncref(mod.pyHandle);
-            return mod.pyHandle;
+        private static bool IsLoadAll(IntPtr fromList)
+        {
+            if (CLRModule.preload)
+            {
+                return false;
+            }
+            if (Runtime.PySequence_Size(fromList) != 1)
+            {
+                return false;
+            }
+            IntPtr fp = Runtime.PySequence_GetItem(fromList, 0);
+            bool res = Runtime.GetManagedString(fp) == "*";
+            Runtime.XDecref(fp);
+            return res;
         }
     }
 }
diff --git a/src/runtime/indexer.cs b/src/runtime/indexer.cs
index 7b6d90ca8..71f7e7aa1 100644
--- a/src/runtime/indexer.cs
+++ b/src/runtime/indexer.cs
@@ -56,7 +56,7 @@ internal void SetItem(IntPtr inst, IntPtr args)
 
         internal bool NeedsDefaultArgs(IntPtr args)
         {
-            int pynargs = Runtime.PyTuple_Size(args);
+            var pynargs = Runtime.PyTuple_Size(args);
             MethodBase[] methods = SetterBinder.GetMethods();
             if (methods.Length == 0)
             {
@@ -72,7 +72,7 @@ internal bool NeedsDefaultArgs(IntPtr args)
                 return false;
             }
 
-            for (int v = pynargs; v < clrnargs; v++)
+            for (var v = pynargs; v < clrnargs; v++)
             {
                 if (pi[v].DefaultValue == DBNull.Value)
                 {
@@ -95,7 +95,7 @@ internal IntPtr GetDefaultArgs(IntPtr args)
             {
                 return Runtime.PyTuple_New(0);
             }
-            int pynargs = Runtime.PyTuple_Size(args);
+            var pynargs = Runtime.PyTuple_Size(args);
 
             // Get the default arg tuple
             MethodBase[] methods = SetterBinder.GetMethods();
diff --git a/src/runtime/interfaceobject.cs b/src/runtime/interfaceobject.cs
index ce1bc9eb0..616ced6bd 100644
--- a/src/runtime/interfaceobject.cs
+++ b/src/runtime/interfaceobject.cs
@@ -36,7 +36,7 @@ static InterfaceObject()
         public static IntPtr tp_new(IntPtr tp, IntPtr args, IntPtr kw)
         {
             var self = (InterfaceObject)GetManagedObject(tp);
-            int nargs = Runtime.PyTuple_Size(args);
+            var nargs = Runtime.PyTuple_Size(args);
             Type type = self.type;
             object obj;
 
diff --git a/src/runtime/interop33.cs b/src/runtime/interop37.cs
similarity index 94%
rename from src/runtime/interop33.cs
rename to src/runtime/interop37.cs
index f684df6c6..d5fc76ad3 100644
--- a/src/runtime/interop33.cs
+++ b/src/runtime/interop37.cs
@@ -2,7 +2,7 @@
 // DO NOT MODIFIY BY HAND.
 
 
-#if PYTHON33
+#if PYTHON37
 using System;
 using System.Collections;
 using System.Collections.Specialized;
@@ -42,7 +42,7 @@ public static int magic()
         public static int tp_print = 0;
         public static int tp_getattr = 0;
         public static int tp_setattr = 0;
-        public static int tp_reserved = 0;
+        public static int tp_as_async = 0;
         public static int tp_repr = 0;
         public static int tp_as_number = 0;
         public static int tp_as_sequence = 0;
@@ -81,6 +81,10 @@ public static int magic()
         public static int tp_weaklist = 0;
         public static int tp_del = 0;
         public static int tp_version_tag = 0;
+        public static int tp_finalize = 0;
+        public static int am_await = 0;
+        public static int am_aiter = 0;
+        public static int am_anext = 0;
         public static int nb_add = 0;
         public static int nb_subtract = 0;
         public static int nb_multiply = 0;
@@ -115,6 +119,8 @@ public static int magic()
         public static int nb_inplace_floor_divide = 0;
         public static int nb_inplace_true_divide = 0;
         public static int nb_index = 0;
+        public static int nb_matrix_multiply = 0;
+        public static int nb_inplace_matrix_multiply = 0;
         public static int mp_length = 0;
         public static int mp_subscript = 0;
         public static int mp_ass_subscript = 0;
diff --git a/src/runtime/iterator.cs b/src/runtime/iterator.cs
index c7c60ab19..f9cf10178 100644
--- a/src/runtime/iterator.cs
+++ b/src/runtime/iterator.cs
@@ -23,9 +23,21 @@ public Iterator(IEnumerator e)
         public static IntPtr tp_iternext(IntPtr ob)
         {
             var self = GetManagedObject(ob) as Iterator;
-            if (!self.iter.MoveNext())
+            try
             {
-                Exceptions.SetError(Exceptions.StopIteration, Runtime.PyNone);
+                if (!self.iter.MoveNext())
+                {
+                    Exceptions.SetError(Exceptions.StopIteration, Runtime.PyNone);
+                    return IntPtr.Zero;
+                }
+            }
+            catch (Exception e)
+            {
+                if (e.InnerException != null)
+                {
+                    e = e.InnerException;
+                }
+                Exceptions.SetError(e);
                 return IntPtr.Zero;
             }
             object item = self.iter.Current;
diff --git a/src/runtime/managedtype.cs b/src/runtime/managedtype.cs
index 9ee8d223b..3191da949 100644
--- a/src/runtime/managedtype.cs
+++ b/src/runtime/managedtype.cs
@@ -28,12 +28,16 @@ internal static ManagedType GetManagedObject(IntPtr ob)
                     tp = ob;
                 }
 
-                var flags = (int)Marshal.ReadIntPtr(tp, TypeOffset.tp_flags);
+                var flags = Util.ReadCLong(tp, TypeOffset.tp_flags);
                 if ((flags & TypeFlags.Managed) != 0)
                 {
                     IntPtr op = tp == ob
                         ? Marshal.ReadIntPtr(tp, TypeOffset.magic())
                         : Marshal.ReadIntPtr(ob, ObjectOffset.magic(ob));
+                    if (op == IntPtr.Zero)
+                    {
+                        return null;
+                    }
                     var gc = (GCHandle)op;
                     return (ManagedType)gc.Target;
                 }
@@ -63,7 +67,7 @@ internal static bool IsManagedType(IntPtr ob)
                     tp = ob;
                 }
 
-                var flags = (int)Marshal.ReadIntPtr(tp, TypeOffset.tp_flags);
+                var flags = Util.ReadCLong(tp, TypeOffset.tp_flags);
                 if ((flags & TypeFlags.Managed) != 0)
                 {
                     return true;
diff --git a/src/runtime/metatype.cs b/src/runtime/metatype.cs
index bfb71e26d..8853c2d5e 100644
--- a/src/runtime/metatype.cs
+++ b/src/runtime/metatype.cs
@@ -29,7 +29,7 @@ public static IntPtr Initialize()
         /// </summary>
         public static IntPtr tp_new(IntPtr tp, IntPtr args, IntPtr kw)
         {
-            int len = Runtime.PyTuple_Size(args);
+            var len = Runtime.PyTuple_Size(args);
             if (len < 3)
             {
                 return Exceptions.RaiseTypeError("invalid argument list");
@@ -105,7 +105,7 @@ public static IntPtr tp_new(IntPtr tp, IntPtr args, IntPtr kw)
             flags |= TypeFlags.BaseType;
             flags |= TypeFlags.Subclass;
             flags |= TypeFlags.HaveGC;
-            Marshal.WriteIntPtr(type, TypeOffset.tp_flags, (IntPtr)flags);
+            Util.WriteCLong(type, TypeOffset.tp_flags, flags);
 
             TypeManager.CopySlot(base_type, type, TypeOffset.tp_dealloc);
 
@@ -157,23 +157,13 @@ public static IntPtr tp_call(IntPtr tp, IntPtr args, IntPtr kw)
                 return IntPtr.Zero;
             }
 
-            IntPtr py__init__ = Runtime.PyString_FromString("__init__");
-            IntPtr type = Runtime.PyObject_TYPE(obj);
-            IntPtr init = Runtime._PyType_Lookup(type, py__init__);
-            Runtime.XDecref(py__init__);
+            var init = Runtime.PyObject_GetAttrString(obj, "__init__");
             Runtime.PyErr_Clear();
 
             if (init != IntPtr.Zero)
             {
-                IntPtr bound = Runtime.GetBoundArgTuple(obj, args);
-                if (bound == IntPtr.Zero)
-                {
-                    Runtime.XDecref(obj);
-                    return IntPtr.Zero;
-                }
-
-                IntPtr result = Runtime.PyObject_Call(init, bound, kw);
-                Runtime.XDecref(bound);
+                IntPtr result = Runtime.PyObject_Call(init, args, kw);
+                Runtime.XDecref(init);
 
                 if (result == IntPtr.Zero)
                 {
@@ -211,7 +201,7 @@ public static int tp_setattro(IntPtr tp, IntPtr name, IntPtr value)
                     IntPtr fp = Marshal.ReadIntPtr(dt, TypeOffset.tp_descr_set);
                     if (fp != IntPtr.Zero)
                     {
-                        return NativeCall.Impl.Int_Call_3(fp, descr, name, value);
+                        return NativeCall.Int_Call_3(fp, descr, name, value);
                     }
                     Exceptions.SetError(Exceptions.AttributeError, "attribute is read-only");
                     return -1;
@@ -247,7 +237,7 @@ public static void tp_dealloc(IntPtr tp)
         {
             // Fix this when we dont cheat on the handle for subclasses!
 
-            var flags = (int)Marshal.ReadIntPtr(tp, TypeOffset.tp_flags);
+            var flags = Util.ReadCLong(tp, TypeOffset.tp_flags);
             if ((flags & TypeFlags.Subclass) == 0)
             {
                 IntPtr gc = Marshal.ReadIntPtr(tp, TypeOffset.magic());
diff --git a/src/runtime/methodbinder.cs b/src/runtime/methodbinder.cs
index f0c58f34f..5e800c36f 100644
--- a/src/runtime/methodbinder.cs
+++ b/src/runtime/methodbinder.cs
@@ -279,7 +279,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
         {
             // loop to find match, return invoker w/ or /wo error
             MethodBase[] _methods = null;
-            int pynargs = Runtime.PyTuple_Size(args);
+            var pynargs = (int)Runtime.PyTuple_Size(args);
             object arg;
             var isGeneric = false;
             ArrayList defaultArgList = null;
@@ -301,9 +301,9 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
                     isGeneric = true;
                 }
                 ParameterInfo[] pi = mi.GetParameters();
-                int clrnargs = pi.Length;
+                var clrnargs = pi.Length;
                 var match = false;
-                int arrayStart = -1;
+                var arrayStart = -1;
                 var outs = 0;
 
                 if (pynargs == clrnargs)
@@ -314,7 +314,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
                 {
                     match = true;
                     defaultArgList = new ArrayList();
-                    for (int v = pynargs; v < clrnargs; v++)
+                    for (var v = pynargs; v < clrnargs; v++)
                     {
                         if (pi[v].DefaultValue == DBNull.Value)
                         {
@@ -338,7 +338,7 @@ internal Binding Bind(IntPtr inst, IntPtr args, IntPtr kw, MethodBase info, Meth
                 {
                     var margs = new object[clrnargs];
 
-                    for (var n = 0; n < clrnargs; n++)
+                    for (int n = 0; n < clrnargs; n++)
                     {
                         IntPtr op;
                         if (n < pynargs)
@@ -507,7 +507,12 @@ internal virtual IntPtr Invoke(IntPtr inst, IntPtr args, IntPtr kw, MethodBase i
 
             if (binding == null)
             {
-                Exceptions.SetError(Exceptions.TypeError, "No method matches given arguments");
+                var value = "No method matches given arguments";
+                if (methodinfo != null && methodinfo.Length > 0)
+                {
+                    value += $" for {methodinfo[0].Name}";
+                }
+                Exceptions.SetError(Exceptions.TypeError, value);
                 return IntPtr.Zero;
             }
 
@@ -596,6 +601,19 @@ internal class MethodSorter : IComparer
     {
         int IComparer.Compare(object m1, object m2)
         {
+            var me1 = (MethodBase)m1;
+            var me2 = (MethodBase)m2;
+            if (me1.DeclaringType != me2.DeclaringType)
+            {
+                // m2's type derives from m1's type, favor m2
+                if (me1.DeclaringType.IsAssignableFrom(me2.DeclaringType))
+                    return 1;
+
+                // m1's type derives from m2's type, favor m1
+                if (me2.DeclaringType.IsAssignableFrom(me1.DeclaringType))
+                    return -1;
+            }
+
             int p1 = MethodBinder.GetPrecedence((MethodBase)m1);
             int p2 = MethodBinder.GetPrecedence((MethodBase)m2);
             if (p1 < p2)
diff --git a/src/runtime/methodbinding.cs b/src/runtime/methodbinding.cs
index 07090a92c..f402f91f8 100644
--- a/src/runtime/methodbinding.cs
+++ b/src/runtime/methodbinding.cs
@@ -56,7 +56,6 @@ public static IntPtr mp_subscript(IntPtr tp, IntPtr idx)
             }
 
             var mb = new MethodBinding(self.m, self.target) { info = mi };
-            Runtime.XIncref(mb.pyHandle);
             return mb.pyHandle;
         }
 
@@ -85,7 +84,6 @@ public static IntPtr tp_getattro(IntPtr ob, IntPtr key)
                 case "__overloads__":
                 case "Overloads":
                     var om = new OverloadMapper(self.m, self.target);
-                    Runtime.XIncref(om.pyHandle);
                     return om.pyHandle;
                 default:
                     return Runtime.PyObject_GenericGetAttr(ob, key);
@@ -106,7 +104,7 @@ public static IntPtr tp_call(IntPtr ob, IntPtr args, IntPtr kw)
             {
                 if (self.info.IsGenericMethod)
                 {
-                    int len = Runtime.PyTuple_Size(args); //FIXME: Never used
+                    var len = Runtime.PyTuple_Size(args); //FIXME: Never used
                     Type[] sigTp = Runtime.PythonArgsToTypeArray(args, true);
                     if (sigTp != null)
                     {
@@ -131,7 +129,7 @@ public static IntPtr tp_call(IntPtr ob, IntPtr args, IntPtr kw)
 
                 if (target == IntPtr.Zero && !self.m.IsStatic())
                 {
-                    int len = Runtime.PyTuple_Size(args);
+                    var len = Runtime.PyTuple_Size(args);
                     if (len < 1)
                     {
                         Exceptions.SetError(Exceptions.TypeError, "not enough arguments");
diff --git a/src/runtime/moduleobject.cs b/src/runtime/moduleobject.cs
index 258d77bac..8af722d29 100644
--- a/src/runtime/moduleobject.cs
+++ b/src/runtime/moduleobject.cs
@@ -190,10 +190,17 @@ public void LoadNames()
             foreach (string name in AssemblyManager.GetNames(_namespace))
             {
                 cache.TryGetValue(name, out m);
-                if (m == null)
+                if (m != null)
                 {
-                    ManagedType attr = GetAttribute(name, true);
+                    continue;
                 }
+                IntPtr attr = Runtime.PyDict_GetItemString(dict, name);
+                // If __dict__ has already set a custom property, skip it.
+                if (attr != IntPtr.Zero)
+                {
+                    continue;
+                }
+                GetAttribute(name, true);
             }
         }
 
@@ -328,6 +335,17 @@ public CLRModule() : base("clr")
             }
         }
 
+        public static void Reset()
+        {
+            hacked = false;
+            interactive_preload = true;
+            preload = false;
+
+            // XXX Test performance of new features //
+            _SuppressDocs = false;
+            _SuppressOverloads = false;
+        }
+
         /// <summary>
         /// The initializing of the preload hook has to happen as late as
         /// possible since sys.ps1 is created after the CLR module is
@@ -395,6 +413,14 @@ public static Assembly AddReference(string name)
             {
                 assembly = AssemblyManager.LoadAssemblyFullPath(name);
             }
+            if (System.IO.File.Exists(name))
+            {
+                var zone = System.Security.Policy.Zone.CreateFromUrl(name);
+                if (zone.SecurityZone != System.Security.SecurityZone.MyComputer)
+                {
+                     throw new Exception($"File is blocked (NTFS Security)");
+                }
+            }
             if (assembly == null)
             {
                 throw new FileNotFoundException($"Unable to find assembly '{name}'.");
@@ -403,6 +429,23 @@ public static Assembly AddReference(string name)
             return assembly;
         }
 
+        /// <summary>
+        /// Get a Type instance for a class object.
+        /// clr.GetClrType(IComparable) gives you the Type for IComparable,
+        /// that you can e.g. perform reflection on. Similar to typeof(IComparable) in C#
+        /// or clr.GetClrType(IComparable) in IronPython.
+        /// 
+        /// </summary>
+        /// <param name="type"></param>
+        /// <returns>The Type object</returns>
+
+        [ModuleFunction]
+        [ForbidPythonThreads]
+        public static Type GetClrType(Type type)
+        {
+            return type;
+        }
+
         [ModuleFunction]
         [ForbidPythonThreads]
         public static string FindAssembly(string name)
diff --git a/src/runtime/nativecall.cs b/src/runtime/nativecall.cs
index 9d1b0f41c..b5bf25dd7 100644
--- a/src/runtime/nativecall.cs
+++ b/src/runtime/nativecall.cs
@@ -23,6 +23,30 @@ namespace Python.Runtime
     /// </summary>
     internal class NativeCall
     {
+#if NETSTANDARD
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        private delegate void Void_1_Delegate(IntPtr a1);
+
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        private delegate int Int_3_Delegate(IntPtr a1, IntPtr a2, IntPtr a3);
+
+        public static void Void_Call_1(IntPtr fp, IntPtr a1)
+        {
+            ((Void_1_Delegate)Marshal.GetDelegateForFunctionPointer(fp, typeof(Void_1_Delegate)))(a1);
+        }
+
+        public static IntPtr Call_3(IntPtr fp, IntPtr a1, IntPtr a2, IntPtr a3)
+        {
+            var d = (Interop.TernaryFunc)Marshal.GetDelegateForFunctionPointer(fp, typeof(Interop.TernaryFunc));
+            return d(a1, a2, a3);
+        }
+
+
+        public static int Int_Call_3(IntPtr fp, IntPtr a1, IntPtr a2, IntPtr a3)
+        {
+            return ((Int_3_Delegate)Marshal.GetDelegateForFunctionPointer(fp, typeof(Int_3_Delegate)))(a1, a2, a3);
+        }
+#else
         private static AssemblyBuilder aBuilder;
         private static ModuleBuilder mBuilder;
 
@@ -132,9 +156,10 @@ public static int Int_Call_3(IntPtr fp, IntPtr a1, IntPtr a2, IntPtr a3)
         {
             return Impl.Int_Call_3(fp, a1, a2, a3);
         }
+#endif
     }
 
-
+#if !NETSTANDARD
     /// <summary>
     /// Defines native call signatures to be generated by NativeCall.
     /// </summary>
@@ -148,4 +173,5 @@ public interface INativeCall
 
         IntPtr Call_3(IntPtr funcPtr, IntPtr a1, IntPtr a2, IntPtr a3);
     }
+#endif
 }
diff --git a/src/runtime/overload.cs b/src/runtime/overload.cs
index 6b48299e8..67868a1b1 100644
--- a/src/runtime/overload.cs
+++ b/src/runtime/overload.cs
@@ -44,7 +44,6 @@ public static IntPtr mp_subscript(IntPtr tp, IntPtr idx)
             }
 
             var mb = new MethodBinding(self.m, self.target) { info = mi };
-            Runtime.XIncref(mb.pyHandle);
             return mb.pyHandle;
         }
 
diff --git a/src/runtime/polyfill/ReflectionPolifills.cs b/src/runtime/polyfill/ReflectionPolifills.cs
new file mode 100644
index 000000000..a7e9c879a
--- /dev/null
+++ b/src/runtime/polyfill/ReflectionPolifills.cs
@@ -0,0 +1,21 @@
+using System;
+using System.Reflection;
+using System.Reflection.Emit;
+
+namespace Python.Runtime
+{
+#if NETSTANDARD
+    public static class ReflectionPolifills
+    {
+        public static AssemblyBuilder DefineDynamicAssembly(this AppDomain appDomain, AssemblyName assemblyName, AssemblyBuilderAccess assemblyBuilderAccess)
+        {
+            return AssemblyBuilder.DefineDynamicAssembly(assemblyName, assemblyBuilderAccess);
+        }
+
+        public static Type CreateType(this TypeBuilder typeBuilder)
+        {
+            return typeBuilder.GetTypeInfo().GetType();
+        }
+    }
+#endif
+}
diff --git a/src/runtime/pyobject.cs b/src/runtime/pyobject.cs
index 47f413409..3b8c71efa 100644
--- a/src/runtime/pyobject.cs
+++ b/src/runtime/pyobject.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Dynamic;
 using System.Linq.Expressions;
 
@@ -12,7 +13,7 @@ namespace Python.Runtime
     /// PY3: https://docs.python.org/3/c-api/object.html
     /// for details.
     /// </summary>
-    public class PyObject : DynamicObject, IDisposable
+    public class PyObject : DynamicObject, IEnumerable, IDisposable
     {
         protected internal IntPtr obj = IntPtr.Zero;
         private bool disposed = false;
@@ -43,6 +44,10 @@ protected PyObject()
 
         ~PyObject()
         {
+            // We needs to disable Finalizers until it's valid implementation.
+            // Current implementation can produce low probability floating bugs.
+            return;
+
             Dispose();
         }
 
@@ -96,6 +101,27 @@ public object AsManagedObject(Type t)
             }
             return result;
         }
+        
+        /// <summary>
+        /// As Method
+        /// </summary>
+        /// <remarks>
+        /// Return a managed object of the given type, based on the
+        /// value of the Python object.
+        /// </remarks>
+        public T As<T>()
+        {
+            if (typeof(T) == typeof(PyObject) || typeof(T) == typeof(object))
+            {
+                return (T)(this as object);
+            }
+            object result;
+            if (!Converter.ToManaged(obj, typeof(T), out result, false))
+            {
+                throw new InvalidCastException("cannot convert object to target type");
+            }
+            return (T)result;
+        }
 
 
         /// <summary>
@@ -493,9 +519,9 @@ public virtual void DelItem(int index)
         /// Returns the length for objects that support the Python sequence
         /// protocol, or 0 if the object does not support the protocol.
         /// </remarks>
-        public virtual int Length()
+        public virtual long Length()
         {
-            int s = Runtime.PyObject_Size(obj);
+            var s = Runtime.PyObject_Size(obj);
             if (s < 0)
             {
                 Runtime.PyErr_Clear();
@@ -781,7 +807,7 @@ public bool IsCallable()
         /// </remarks>
         public bool IsIterable()
         {
-            return Runtime.PyIter_Check(obj);
+            return Runtime.PyObject_IsIterable(obj);
         }
 
 
@@ -884,7 +910,7 @@ public override bool Equals(object o)
         /// </remarks>
         public override int GetHashCode()
         {
-            return Runtime.PyObject_Hash(obj).ToInt32();
+            return ((ulong)Runtime.PyObject_Hash(obj)).GetHashCode();
         }
 
 
@@ -915,6 +941,34 @@ public override bool TrySetMember(SetMemberBinder binder, object value)
             return true;
         }
 
+        private void GetArgs(object[] inargs, CallInfo callInfo, out PyTuple args, out PyDict kwargs)
+        {
+            if (callInfo == null || callInfo.ArgumentNames.Count == 0)
+            {
+                GetArgs(inargs, out args, out kwargs);
+                return;
+            }
+
+            // Support for .net named arguments
+            var namedArgumentCount = callInfo.ArgumentNames.Count;
+            var regularArgumentCount = callInfo.ArgumentCount - namedArgumentCount;
+
+            var argTuple = Runtime.PyTuple_New(regularArgumentCount);
+            for (int i = 0; i < regularArgumentCount; ++i)
+            {
+                AddArgument(argTuple, i, inargs[i]);
+            }
+            args = new PyTuple(argTuple);
+
+            var namedArgs = new object[namedArgumentCount * 2];
+            for (int i = 0; i < namedArgumentCount; ++i)
+            {
+                namedArgs[i * 2] = callInfo.ArgumentNames[i];
+                namedArgs[i * 2 + 1] = inargs[regularArgumentCount + i];
+            }
+            kwargs = Py.kw(namedArgs);
+        }
+
         private void GetArgs(object[] inargs, out PyTuple args, out PyDict kwargs)
         {
             int arg_count;
@@ -925,22 +979,10 @@ private void GetArgs(object[] inargs, out PyTuple args, out PyDict kwargs)
             IntPtr argtuple = Runtime.PyTuple_New(arg_count);
             for (var i = 0; i < arg_count; i++)
             {
-                IntPtr ptr;
-                if (inargs[i] is PyObject)
-                {
-                    ptr = ((PyObject)inargs[i]).Handle;
-                    Runtime.XIncref(ptr);
-                }
-                else
-                {
-                    ptr = Converter.ToPython(inargs[i], inargs[i]?.GetType());
-                }
-                if (Runtime.PyTuple_SetItem(argtuple, i, ptr) < 0)
-                {
-                    throw new PythonException();
-                }
+                AddArgument(argtuple, i, inargs[i]);
             }
             args = new PyTuple(argtuple);
+
             kwargs = null;
             for (int i = arg_count; i < inargs.Length; i++)
             {
@@ -959,6 +1001,32 @@ private void GetArgs(object[] inargs, out PyTuple args, out PyDict kwargs)
             }
         }
 
+        private static void AddArgument(IntPtr argtuple, int i, object target)
+        {
+            IntPtr ptr = GetPythonObject(target);
+
+            if (Runtime.PyTuple_SetItem(argtuple, i, ptr) < 0)
+            {
+                throw new PythonException();
+            }
+        }
+
+        private static IntPtr GetPythonObject(object target)
+        {
+            IntPtr ptr;
+            if (target is PyObject)
+            {
+                ptr = ((PyObject)target).Handle;
+                Runtime.XIncref(ptr);
+            }
+            else
+            {
+                ptr = Converter.ToPython(target, target?.GetType());
+            }
+
+            return ptr;
+        }
+
         public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result)
         {
             if (this.HasAttr(binder.Name) && this.GetAttr(binder.Name).IsCallable())
@@ -967,7 +1035,7 @@ public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, o
                 PyDict kwargs = null;
                 try
                 {
-                    GetArgs(args, out pyargs, out kwargs);
+                    GetArgs(args, binder.CallInfo, out pyargs, out kwargs);
                     result = CheckNone(InvokeMethod(binder.Name, pyargs, kwargs));
                 }
                 finally
@@ -997,7 +1065,7 @@ public override bool TryInvoke(InvokeBinder binder, object[] args, out object re
                 PyDict kwargs = null;
                 try
                 {
-                    GetArgs(args, out pyargs, out kwargs);
+                    GetArgs(args, binder.CallInfo, out pyargs, out kwargs);
                     result = CheckNone(Invoke(pyargs, kwargs));
                 }
                 finally
@@ -1171,5 +1239,20 @@ public override bool TryUnaryOperation(UnaryOperationBinder binder, out object r
             result = CheckNone(new PyObject(res));
             return true;
         }
+
+        /// <summary>
+        /// Returns the enumeration of all dynamic member names.
+        /// </summary>
+        /// <remarks>
+        /// This method exists for debugging purposes only.
+        /// </remarks>
+        /// <returns>A sequence that contains dynamic member names.</returns>
+        public override IEnumerable<string> GetDynamicMemberNames()
+        {
+            foreach (PyObject pyObj in Dir())
+            {
+                yield return pyObj.ToString();
+            }
+        }
     }
 }
diff --git a/src/runtime/pyscope.cs b/src/runtime/pyscope.cs
new file mode 100644
index 000000000..8e6957855
--- /dev/null
+++ b/src/runtime/pyscope.cs
@@ -0,0 +1,662 @@
+using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Dynamic;
+
+namespace Python.Runtime
+{
+    public class PyScopeException : Exception
+    {
+        public PyScopeException(string message)
+            : base(message)
+        {
+
+        }
+    }
+
+    /// <summary>
+    /// Classes/methods have this attribute must be used with GIL obtained.
+    /// </summary>
+    public class PyGILAttribute : Attribute
+    {
+    }
+
+    [PyGIL]
+    public class PyScope : DynamicObject, IDisposable
+    {
+        public readonly string Name;
+
+        /// <summary>
+        /// the python Module object the scope associated with.
+        /// </summary>
+        internal readonly IntPtr obj;
+
+        /// <summary>
+        /// the variable dict of the scope.
+        /// </summary>
+        internal readonly IntPtr variables;
+
+        private bool _isDisposed;
+
+        /// <summary>
+        /// The Manager this scope associated with.
+        /// It provides scopes this scope can import.
+        /// </summary>
+        internal readonly PyScopeManager Manager;
+
+        /// <summary>
+        /// event which will be triggered after the scope disposed.
+        /// </summary>
+        public event Action<PyScope> OnDispose;
+
+        /// <summary>
+        /// Constructor
+        /// </summary>
+        /// <remarks>
+        /// Create a scope based on a Python Module.
+        /// </remarks>
+        internal PyScope(IntPtr ptr, PyScopeManager manager)
+        {
+            if (!Runtime.PyType_IsSubtype(Runtime.PyObject_TYPE(ptr), Runtime.PyModuleType))
+            {
+                throw new PyScopeException("object is not a module");
+            }
+            Manager = manager ?? PyScopeManager.Global;
+            obj = ptr;
+            //Refcount of the variables not increase
+            variables = Runtime.PyModule_GetDict(obj);
+            Runtime.CheckExceptionOccurred();
+
+            Runtime.PyDict_SetItemString(
+                variables, "__builtins__",
+                Runtime.PyEval_GetBuiltins()
+            );
+            this.Name = this.Get<string>("__name__");
+        }
+
+        /// <summary>
+        /// return the variable dict of the scope.
+        /// </summary>
+        /// <returns></returns>
+        public PyDict Variables()
+        {
+            Runtime.XIncref(variables);
+            return new PyDict(variables);
+        }
+
+        /// <summary>
+        /// Create a scope, and import all from this scope
+        /// </summary>
+        /// <returns></returns>
+        public PyScope NewScope()
+        {
+            var scope = Manager.Create();
+            scope.ImportAll(this);
+            return scope;
+        }
+
+        /// <summary>
+        /// Import method
+        /// </summary>
+        /// <remarks>
+        /// Import a scope or a module of given name,
+        /// scope will be looked up first.
+        /// </remarks>
+        public dynamic Import(string name, string asname = null)
+        {
+            Check();
+            if (String.IsNullOrEmpty(asname))
+            {
+                asname = name;
+            }
+            PyScope scope;
+            Manager.TryGet(name, out scope);
+            if (scope != null)
+            {
+                Import(scope, asname);
+                return scope;
+            }
+            else
+            {
+                PyObject module = PythonEngine.ImportModule(name);
+                Import(module, asname);
+                return module;
+            }
+        }
+
+        /// <summary>
+        /// Import method
+        /// </summary>
+        /// <remarks>
+        /// Import a scope as a variable of given name.
+        /// </remarks>
+        public void Import(PyScope scope, string asname)
+        {
+            this.Set(asname, scope.obj);
+        }
+
+        /// <summary>
+        /// Import Method
+        /// </summary>
+        /// <remarks>
+        /// The 'import .. as ..' statement in Python.
+        /// Import a module as a variable into the scope.
+        /// </remarks>
+        public void Import(PyObject module, string asname = null)
+        {
+            if (String.IsNullOrEmpty(asname))
+            {
+                asname = module.GetAttr("__name__").As<string>();
+            }
+            Set(asname, module);
+        }
+
+        /// <summary>
+        /// ImportAll Method
+        /// </summary>
+        /// <remarks>
+        /// The 'import * from ..' statement in Python.
+        /// Import all content of a scope/module of given name into the scope, scope will be looked up first.
+        /// </remarks>
+        public void ImportAll(string name)
+        {
+            PyScope scope;
+            Manager.TryGet(name, out scope);
+            if (scope != null)
+            {
+                ImportAll(scope);
+                return;
+            }
+            else
+            {
+                PyObject module = PythonEngine.ImportModule(name);
+                ImportAll(module);
+            }
+        }
+
+        /// <summary>
+        /// ImportAll Method
+        /// </summary>
+        /// <remarks>
+        /// Import all variables of the scope into this scope.
+        /// </remarks>
+        public void ImportAll(PyScope scope)
+        {
+            int result = Runtime.PyDict_Update(variables, scope.variables);
+            if (result < 0)
+            {
+                throw new PythonException();
+            }
+        }
+
+        /// <summary>
+        /// ImportAll Method
+        /// </summary>
+        /// <remarks>
+        /// Import all variables of the module into this scope.
+        /// </remarks>
+        public void ImportAll(PyObject module)
+        {
+            if (Runtime.PyObject_Type(module.obj) != Runtime.PyModuleType)
+            {
+                throw new PyScopeException("object is not a module");
+            }
+            var module_dict = Runtime.PyModule_GetDict(module.obj);
+            int result = Runtime.PyDict_Update(variables, module_dict);
+            if (result < 0)
+            {
+                throw new PythonException();
+            }
+        }
+
+        /// <summary>
+        /// ImportAll Method
+        /// </summary>
+        /// <remarks>
+        /// Import all variables in the dictionary into this scope.
+        /// </remarks>
+        public void ImportAll(PyDict dict)
+        {
+            int result = Runtime.PyDict_Update(variables, dict.obj);
+            if (result < 0)
+            {
+                throw new PythonException();
+            }
+        }
+
+        /// <summary>
+        /// Execute method
+        /// </summary>
+        /// <remarks>
+        /// Execute a Python ast and return the result as a PyObject.
+        /// The ast can be either an expression or stmts.
+        /// </remarks>
+        public PyObject Execute(PyObject script, PyDict locals = null)
+        {
+            Check();
+            IntPtr _locals = locals == null ? variables : locals.obj;
+            IntPtr ptr = Runtime.PyEval_EvalCode(script.Handle, variables, _locals);
+            Runtime.CheckExceptionOccurred();
+            if (ptr == Runtime.PyNone)
+            {
+                Runtime.XDecref(ptr);
+                return null;
+            }
+            return new PyObject(ptr);
+        }
+
+        /// <summary>
+        /// Execute method
+        /// </summary>
+        /// <remarks>
+        /// Execute a Python ast and return the result as a PyObject,
+        /// and convert the result to a Managed Object of given type.
+        /// The ast can be either an expression or stmts.
+        /// </remarks>
+        public T Execute<T>(PyObject script, PyDict locals = null)
+        {
+            Check();
+            PyObject pyObj = Execute(script, locals);
+            if (pyObj == null)
+            {
+                return default(T);
+            }
+            var obj = pyObj.As<T>();
+            return obj;
+        }
+
+        /// <summary>
+        /// Eval method
+        /// </summary>
+        /// <remarks>
+        /// Evaluate a Python expression and return the result as a PyObject
+        /// or null if an exception is raised.
+        /// </remarks>
+        public PyObject Eval(string code, PyDict locals = null)
+        {
+            Check();
+            IntPtr _locals = locals == null ? variables : locals.obj;
+            var flag = (IntPtr)Runtime.Py_eval_input;
+            IntPtr ptr = Runtime.PyRun_String(
+                code, flag, variables, _locals
+            );
+            Runtime.CheckExceptionOccurred();
+            return new PyObject(ptr);
+        }
+
+        /// <summary>
+        /// Evaluate a Python expression
+        /// </summary>
+        /// <remarks>
+        /// Evaluate a Python expression
+        /// and  convert the result to a Managed Object of given type.
+        /// </remarks>
+        public T Eval<T>(string code, PyDict locals = null)
+        {
+            Check();
+            PyObject pyObj = Eval(code, locals);
+            var obj = pyObj.As<T>();
+            return obj;
+        }
+
+        /// <summary>
+        /// Exec Method
+        /// </summary>
+        /// <remarks>
+        /// Exec a Python script and save its local variables in the current local variable dict.
+        /// </remarks>
+        public void Exec(string code, PyDict locals = null)
+        {
+            Check();
+            IntPtr _locals = locals == null ? variables : locals.obj;
+            Exec(code, variables, _locals);
+        }
+
+        private void Exec(string code, IntPtr _globals, IntPtr _locals)
+        {
+            var flag = (IntPtr)Runtime.Py_file_input;
+            IntPtr ptr = Runtime.PyRun_String(
+                code, flag, _globals, _locals
+            );
+            Runtime.CheckExceptionOccurred();
+            if (ptr != Runtime.PyNone)
+            {
+                throw new PythonException();
+            }
+            Runtime.XDecref(ptr);
+        }
+
+        /// <summary>
+        /// Set Variable Method
+        /// </summary>
+        /// <remarks>
+        /// Add a new variable to the variables dict if it not exist
+        /// or update its value if the variable exists.
+        /// </remarks>
+        public void Set(string name, object value)
+        {
+            IntPtr _value = Converter.ToPython(value, value?.GetType());
+            Set(name, _value);
+            Runtime.XDecref(_value);
+        }
+
+        private void Set(string name, IntPtr value)
+        {
+            Check();
+            using (var pyKey = new PyString(name))
+            {
+                int r = Runtime.PyObject_SetItem(variables, pyKey.obj, value);
+                if (r < 0)
+                {
+                    throw new PythonException();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Remove Method
+        /// </summary>
+        /// <remarks>
+        /// Remove a variable from the variables dict.
+        /// </remarks>
+        public void Remove(string name)
+        {
+            Check();
+            using (var pyKey = new PyString(name))
+            {
+                int r = Runtime.PyObject_DelItem(variables, pyKey.obj);
+                if (r < 0)
+                {
+                    throw new PythonException();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Contains Method
+        /// </summary>
+        /// <remarks>
+        /// Returns true if the variable exists in the scope.
+        /// </remarks>
+        public bool Contains(string name)
+        {
+            Check();
+            using (var pyKey = new PyString(name))
+            {
+                return Runtime.PyMapping_HasKey(variables, pyKey.obj) != 0;
+            }
+        }
+
+        /// <summary>
+        /// Get Method
+        /// </summary>
+        /// <remarks>
+        /// Returns the value of the variable of given name.
+        /// If the variable does not exist, throw an Exception.
+        /// </remarks>
+        public PyObject Get(string name)
+        {
+            PyObject scope;
+            var state = TryGet(name, out scope);
+            if (!state)
+            {
+                throw new PyScopeException($"The scope of name '{Name}' has no attribute '{name}'");
+            }
+            return scope;
+        }
+
+        /// <summary>
+        /// TryGet Method
+        /// </summary>
+        /// <remarks>
+        /// Returns the value of the variable, local variable first.
+        /// If the variable does not exist, return null.
+        /// </remarks>
+        public bool TryGet(string name, out PyObject value)
+        {
+            Check();
+            using (var pyKey = new PyString(name))
+            {
+                if (Runtime.PyMapping_HasKey(variables, pyKey.obj) != 0)
+                {
+                    IntPtr op = Runtime.PyObject_GetItem(variables, pyKey.obj);
+                    if (op == IntPtr.Zero)
+                    {
+                        throw new PythonException();
+                    }
+                    if (op == Runtime.PyNone)
+                    {
+                        Runtime.XDecref(op);
+                        value = null;
+                        return true;
+                    }
+                    value = new PyObject(op);
+                    return true;
+                }
+                else
+                {
+                    value = null;
+                    return false;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Get Method
+        /// </summary>
+        /// <remarks>
+        /// Obtain the value of the variable of given name,
+        /// and convert the result to a Managed Object of given type.
+        /// If the variable does not exist, throw an Exception.
+        /// </remarks>
+        public T Get<T>(string name)
+        {
+            Check();
+            PyObject pyObj = Get(name);
+            if (pyObj == null)
+            {
+                return default(T);
+            }
+            return pyObj.As<T>();
+        }
+
+        /// <summary>
+        /// TryGet Method
+        /// </summary>
+        /// <remarks>
+        /// Obtain the value of the variable of given name,
+        /// and convert the result to a Managed Object of given type.
+        /// If the variable does not exist, return false.
+        /// </remarks>
+        public bool TryGet<T>(string name, out T value)
+        {
+            Check();
+            PyObject pyObj;
+            var result = TryGet(name, out pyObj);
+            if (!result)
+            {
+                value = default(T);
+                return false;
+            }
+            if (pyObj == null)
+            {
+                if (typeof(T).IsValueType)
+                {
+                    throw new PyScopeException($"The value of the attribute '{name}' is None which cannot be convert to '{typeof(T).ToString()}'");
+                }
+                else
+                {
+                    value = default(T);
+                    return true;
+                }
+            }
+            value = pyObj.As<T>();
+            return true;
+        }
+
+        public override bool TryGetMember(GetMemberBinder binder, out object result)
+        {
+            result = this.Get(binder.Name);
+            return true;
+        }
+
+        public override bool TrySetMember(SetMemberBinder binder, object value)
+        {
+            this.Set(binder.Name, value);
+            return true;
+        }
+
+        private void Check()
+        {
+            if (_isDisposed)
+            {
+                throw new PyScopeException($"The scope of name '{Name}' object has been disposed");
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_isDisposed)
+            {
+                return;
+            }
+            _isDisposed = true;
+            Runtime.XDecref(obj);
+            this.OnDispose?.Invoke(this);
+        }
+
+        ~PyScope()
+        {
+            // We needs to disable Finalizers until it's valid implementation.
+            // Current implementation can produce low probability floating bugs.
+            return;
+
+            Dispose();
+        }
+    }
+
+    public class PyScopeManager
+    {
+        public static PyScopeManager Global;
+
+        private Dictionary<string, PyScope> NamedScopes = new Dictionary<string, PyScope>();
+
+        internal static void Reset()
+        {
+            Global = new PyScopeManager();
+        }
+
+        internal PyScope NewScope(string name)
+        {
+            if (name == null)
+            {
+                name = "";
+            }
+            var module = Runtime.PyModule_New(name);
+            if (module == IntPtr.Zero)
+            {
+                throw new PythonException();
+            }
+            return new PyScope(module, this);
+        }
+
+        /// <summary>
+        /// Create Method
+        /// </summary>
+        /// <remarks>
+        /// Create an anonymous scope.
+        /// </remarks>
+        [PyGIL]
+        public PyScope Create()
+        {
+            var scope = this.NewScope(null);
+            return scope;
+        }
+
+        /// <summary>
+        /// Create Method
+        /// </summary>
+        /// <remarks>
+        /// Create an named scope of given name.
+        /// </remarks>
+        [PyGIL]
+        public PyScope Create(string name)
+        {
+            if (String.IsNullOrEmpty(name))
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+            if (name != null && Contains(name))
+            {
+                throw new PyScopeException($"A scope of name '{name}' does already exist");
+            }
+            var scope = this.NewScope(name);
+            scope.OnDispose += Remove;
+            NamedScopes[name] = scope;
+            return scope;
+        }
+
+        /// <summary>
+        /// Contains Method
+        /// </summary>
+        /// <remarks>
+        /// return true if the scope exists in this manager.
+        /// </remarks>
+        public bool Contains(string name)
+        {
+            return NamedScopes.ContainsKey(name);
+        }
+
+        /// <summary>
+        /// Get Method
+        /// </summary>
+        /// <remarks>
+        /// Find the scope in this manager.
+        /// If the scope not exist, an Exception will be thrown.
+        /// </remarks>
+        public PyScope Get(string name)
+        {
+            if (String.IsNullOrEmpty(name))
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+            if (NamedScopes.ContainsKey(name))
+            {
+                return NamedScopes[name];
+            }
+            throw new PyScopeException($"There is no scope named '{name}' registered in this manager");
+        }
+
+        /// <summary>
+        /// Get Method
+        /// </summary>
+        /// <remarks>
+        /// Try to find the scope in this manager.
+        /// </remarks>
+        public bool TryGet(string name, out PyScope scope)
+        {
+            return NamedScopes.TryGetValue(name, out scope);
+        }
+
+        /// <summary>
+        /// Remove Method
+        /// </summary>
+        /// <remarks>
+        /// remove the scope from this manager.
+        /// </remarks>
+        public void Remove(PyScope scope)
+        {
+            NamedScopes.Remove(scope.Name);
+        }
+
+        [PyGIL]
+        public void Clear()
+        {
+            var scopes = NamedScopes.Values.ToList();
+            foreach (var scope in scopes)
+            {
+                scope.Dispose();
+            }
+        }
+    }
+}
diff --git a/src/runtime/pythonengine.cs b/src/runtime/pythonengine.cs
index 1fd3b239a..c1b663d22 100644
--- a/src/runtime/pythonengine.cs
+++ b/src/runtime/pythonengine.cs
@@ -140,9 +140,9 @@ public static void Initialize()
             Initialize(setSysArgv: true);
         }
 
-        public static void Initialize(bool setSysArgv = true)
+        public static void Initialize(bool setSysArgv = true, bool initSigs = false)
         {
-            Initialize(Enumerable.Empty<string>(), setSysArgv: setSysArgv);
+            Initialize(Enumerable.Empty<string>(), setSysArgv: setSysArgv, initSigs: initSigs);
         }
 
         /// <summary>
@@ -153,8 +153,9 @@ public static void Initialize(bool setSysArgv = true)
         /// more than once, though initialization will only happen on the
         /// first call. It is *not* necessary to hold the Python global
         /// interpreter lock (GIL) to call this method.
+        /// initSigs can be set to 1 to do default python signal configuration. This will override the way signals are handled by the application.
         /// </remarks>
-        public static void Initialize(IEnumerable<string> args, bool setSysArgv = true)
+        public static void Initialize(IEnumerable<string> args, bool setSysArgv = true, bool initSigs = false)
         {
             if (!initialized)
             {
@@ -164,10 +165,20 @@ public static void Initialize(IEnumerable<string> args, bool setSysArgv = true)
                 // during an initial "import clr", and the world ends shortly thereafter.
                 // This is probably masking some bad mojo happening somewhere in Runtime.Initialize().
                 delegateManager = new DelegateManager();
-                Runtime.Initialize();
+                Runtime.Initialize(initSigs);
                 initialized = true;
                 Exceptions.Clear();
 
+                // Make sure we clean up properly on app domain unload.
+                AppDomain.CurrentDomain.DomainUnload += OnDomainUnload;
+
+                // Remember to shut down the runtime.
+                AddShutdownHandler(Runtime.Shutdown);
+
+                // The global scope gets used implicitly quite early on, remember
+                // to clear it out when we shut down.
+                AddShutdownHandler(PyScopeManager.Global.Clear);
+
                 if (setSysArgv)
                 {
                     Py.SetArgv(args);
@@ -223,6 +234,11 @@ public static void Initialize(IEnumerable<string> args, bool setSysArgv = true)
             }
         }
 
+        static void OnDomainUnload(object _, EventArgs __)
+        {
+            Shutdown();
+        }
+
         /// <summary>
         /// A helper to perform initialization from the context of an active
         /// CPython interpreter process - this bootstraps the managed runtime
@@ -294,18 +310,81 @@ public static void Shutdown()
         {
             if (initialized)
             {
-                Marshal.FreeHGlobal(_pythonHome);
-                _pythonHome = IntPtr.Zero;
-                Marshal.FreeHGlobal(_programName);
-                _programName = IntPtr.Zero;
-                Marshal.FreeHGlobal(_pythonPath);
-                _pythonPath = IntPtr.Zero;
+                PyScopeManager.Global.Clear();
+                
+                // If the shutdown handlers trigger a domain unload,
+                // don't call shutdown again.
+                AppDomain.CurrentDomain.DomainUnload -= OnDomainUnload;
+
+                ExecuteShutdownHandlers();
 
-                Runtime.Shutdown();
                 initialized = false;
             }
         }
 
+        /// <summary>
+        /// Called when the engine is shut down.
+        ///
+        /// Shutdown handlers are run in reverse order they were added, so that
+        /// resources available when running a shutdown handler are the same as
+        /// what was available when it was added.
+        /// </summary>
+        public delegate void ShutdownHandler();
+
+        static List<ShutdownHandler> ShutdownHandlers = new List<ShutdownHandler>();
+
+        /// <summary>
+        /// Add a function to be called when the engine is shut down.
+        ///
+        /// Shutdown handlers are executed in the opposite order they were
+        /// added, so that you can be sure that everything that was initialized
+        /// when you added the handler is still initialized when you need to shut
+        /// down.
+        ///
+        /// If the same shutdown handler is added several times, it will be run
+        /// several times.
+        ///
+        /// Don't add shutdown handlers while running a shutdown handler.
+        /// </summary>
+        public static void AddShutdownHandler(ShutdownHandler handler)
+        {
+            ShutdownHandlers.Add(handler);
+        }
+
+        /// <summary>
+        /// Remove a shutdown handler.
+        ///
+        /// If the same shutdown handler is added several times, only the last
+        /// one is removed.
+        ///
+        /// Don't remove shutdown handlers while running a shutdown handler.
+        /// </summary>
+        public static void RemoveShutdownHandler(ShutdownHandler handler)
+        {
+            for (int index = ShutdownHandlers.Count - 1; index >= 0; --index)
+            {
+                if (ShutdownHandlers[index] == handler)
+                {
+                    ShutdownHandlers.RemoveAt(index);
+                    break;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Run all the shutdown handlers.
+        ///
+        /// They're run in opposite order they were added.
+        /// </summary>
+        static void ExecuteShutdownHandlers()
+        {
+            while(ShutdownHandlers.Count > 0)
+            {
+                var handler = ShutdownHandlers[ShutdownHandlers.Count - 1];
+                ShutdownHandlers.RemoveAt(ShutdownHandlers.Count - 1);
+                handler();
+            }
+        }
 
         /// <summary>
         /// AcquireLock Method
@@ -421,6 +500,13 @@ public static PyObject ModuleFromString(string name, string code)
             return new PyObject(m);
         }
 
+        public static PyObject Compile(string code, string filename = "", RunFlagType mode = RunFlagType.File)
+        {
+            var flag = (IntPtr)mode;
+            IntPtr ptr = Runtime.Py_CompileString(code, filename, flag);
+            Runtime.CheckExceptionOccurred();
+            return new PyObject(ptr);
+        }
 
         /// <summary>
         /// Eval Method
@@ -488,12 +574,10 @@ internal static PyObject RunString(string code, IntPtr? globals, IntPtr? locals,
                     borrowedGlobals = false;
                 }
             }
-
-            var borrowedLocals = true;
+            
             if (locals == null)
             {
-                locals = Runtime.PyDict_New();
-                borrowedLocals = false;
+                locals = globals;
             }
 
             try
@@ -508,10 +592,6 @@ internal static PyObject RunString(string code, IntPtr? globals, IntPtr? locals,
             }
             finally
             {
-                if (!borrowedLocals)
-                {
-                    Runtime.XDecref(locals.Value);
-                }
                 if (!borrowedGlobals)
                 {
                     Runtime.XDecref(globals.Value);
@@ -539,6 +619,18 @@ public static GILState GIL()
             return new GILState();
         }
 
+        public static PyScope CreateScope()
+        {
+            var scope = PyScopeManager.Global.Create();
+            return scope;
+        }
+
+        public static PyScope CreateScope(string name)
+        {
+            var scope = PyScopeManager.Global.Create(name);
+            return scope;
+        }
+        
         public class GILState : IDisposable
         {
             private IntPtr state;
@@ -632,5 +724,34 @@ public static void SetArgv(IEnumerable<string> argv)
                 Runtime.CheckExceptionOccurred();
             }
         }
+
+        public static void With(PyObject obj, Action<dynamic> Body)
+        {
+            // Behavior described here: 
+            // https://docs.python.org/2/reference/datamodel.html#with-statement-context-managers
+
+            IntPtr type = Runtime.PyNone;
+            IntPtr val = Runtime.PyNone;
+            IntPtr traceBack = Runtime.PyNone;
+            PythonException ex = null;
+
+            try
+            {
+                PyObject enterResult = obj.InvokeMethod("__enter__");
+
+                Body(enterResult);
+            }
+            catch (PythonException e)
+            {
+                ex = e;
+                type = ex.PyType;
+                val = ex.PyValue;
+                traceBack = ex.PyTB;
+            }
+
+            var exitResult = obj.InvokeMethod("__exit__", new PyObject(type), new PyObject(val), new PyObject(traceBack));
+
+            if (ex != null && !exitResult.IsTrue()) throw ex;
+        }
     }
 }
diff --git a/src/runtime/pythonexception.cs b/src/runtime/pythonexception.cs
index 4fe07f3cf..ded7fbeb5 100644
--- a/src/runtime/pythonexception.cs
+++ b/src/runtime/pythonexception.cs
@@ -13,6 +13,7 @@ public class PythonException : System.Exception
         private IntPtr _pyTB = IntPtr.Zero;
         private string _tb = "";
         private string _message = "";
+        private string _pythonTypeName = "";
         private bool disposed = false;
 
         public PythonException()
@@ -33,6 +34,8 @@ public PythonException()
                     type = pyTypeName.ToString();
                 }
 
+                _pythonTypeName = type;
+
                 Runtime.XIncref(_pyValue);
                 using (var pyValue = new PyObject(_pyValue))
                 {
@@ -57,6 +60,10 @@ public PythonException()
 
         ~PythonException()
         {
+            // We needs to disable Finalizers until it's valid implementation.
+            // Current implementation can produce low probability floating bugs.
+            return;
+
             Dispose();
         }
 
@@ -128,6 +135,13 @@ public override string StackTrace
             get { return _tb; }
         }
 
+        /// <summary>
+        /// Python error type name.
+        /// </summary>
+        public string PythonTypeName
+        {
+            get { return _pythonTypeName; }
+        }
 
         /// <summary>
         /// Dispose Method
diff --git a/src/runtime/resources/clr.py b/src/runtime/resources/clr.py
index 91f1f6b15..e708a54ac 100644
--- a/src/runtime/resources/clr.py
+++ b/src/runtime/resources/clr.py
@@ -2,7 +2,7 @@
 Code in this module gets loaded into the main clr module.
 """
 
-__version__ = "2.3.0"
+__version__ = "2.4.0.dev0"
 
 
 class clrproperty(object):
diff --git a/src/runtime/runtime.cs b/src/runtime/runtime.cs
index 346ea745f..863eb4034 100644
--- a/src/runtime/runtime.cs
+++ b/src/runtime/runtime.cs
@@ -2,6 +2,7 @@
 using System.Runtime.InteropServices;
 using System.Security;
 using System.Text;
+using System.Collections.Generic;
 
 namespace Python.Runtime
 {
@@ -9,6 +10,27 @@ namespace Python.Runtime
     internal static class NativeMethods
     {
 #if MONO_LINUX || MONO_OSX
+#if NETSTANDARD
+        private static int RTLD_NOW = 0x2;
+#if MONO_LINUX
+        private static int RTLD_GLOBAL = 0x100;
+        private static IntPtr RTLD_DEFAULT = IntPtr.Zero;
+        private const string NativeDll = "libdl.so";
+        public static IntPtr LoadLibrary(string fileName)
+        {
+            return dlopen($"lib{fileName}.so", RTLD_NOW | RTLD_GLOBAL);
+        }
+#elif MONO_OSX
+        private static int RTLD_GLOBAL = 0x8;
+        private const string NativeDll = "/usr/lib/libSystem.dylib";
+        private static IntPtr RTLD_DEFAULT = new IntPtr(-2);
+
+        public static IntPtr LoadLibrary(string fileName)
+        {
+            return dlopen($"lib{fileName}.dylib", RTLD_NOW | RTLD_GLOBAL);
+        }
+#endif
+#else
         private static int RTLD_NOW = 0x2;
         private static int RTLD_SHARED = 0x20;
 #if MONO_OSX
@@ -23,6 +45,8 @@ public static IntPtr LoadLibrary(string fileName)
         {
             return dlopen(fileName, RTLD_NOW | RTLD_SHARED);
         }
+#endif
+
 
         public static void FreeLibrary(IntPtr handle)
         {
@@ -48,16 +72,16 @@ public static IntPtr GetProcAddress(IntPtr dllHandle, string name)
             return res;
         }
 
-        [DllImport(NativeDll)]
-        private static extern IntPtr dlopen(String fileName, int flags);
+        [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
+        public static extern IntPtr dlopen(String fileName, int flags);
 
-        [DllImport(NativeDll)]
+        [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
         private static extern IntPtr dlsym(IntPtr handle, String symbol);
 
-        [DllImport(NativeDll)]
+        [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
         private static extern int dlclose(IntPtr handle);
 
-        [DllImport(NativeDll)]
+        [DllImport(NativeDll, CallingConvention = CallingConvention.Cdecl)]
         private static extern IntPtr dlerror();
 #else // Windows
         private const string NativeDll = "kernel32.dll";
@@ -80,8 +104,14 @@ public static IntPtr GetProcAddress(IntPtr dllHandle, string name)
     /// </summary>
     public class Runtime
     {
+        // C# compiler copies constants to the assemblies that references this library.
+        // We needs to replace all public constants to static readonly fields to allow 
+        // binary substitution of different Python.Runtime.dll builds in a target application.
+
+        public static int UCS => _UCS;
+
 #if UCS4
-        public const int UCS = 4;
+        internal const int _UCS = 4;
 
         /// <summary>
         /// EntryPoint to be used in DllImport to map to correct Unicode
@@ -89,7 +119,7 @@ public class Runtime
         /// </summary>
         private const string PyUnicodeEntryPoint = "PyUnicodeUCS4_";
 #elif UCS2
-        public const int UCS = 2;
+        internal const int _UCS = 2;
 
         /// <summary>
         /// EntryPoint to be used in DllImport to map to correct Unicode
@@ -100,32 +130,36 @@ public class Runtime
 #error You must define either UCS2 or UCS4!
 #endif
 
+        // C# compiler copies constants to the assemblies that references this library.
+        // We needs to replace all public constants to static readonly fields to allow 
+        // binary substitution of different Python.Runtime.dll builds in a target application.
+
+        public static string pyversion => _pyversion;
+        public static string pyver => _pyver;
+
 #if PYTHON27
-        public const string pyversion = "2.7";
-        public const string pyver = "27";
-#elif PYTHON33
-        public const string pyversion = "3.3";
-        public const string pyver = "33";
+        internal const string _pyversion = "2.7";
+        internal const string _pyver = "27";
 #elif PYTHON34
-        public const string pyversion = "3.4";
-        public const string pyver = "34";
+        internal const string _pyversion = "3.4";
+        internal const string _pyver = "34";
 #elif PYTHON35
-        public const string pyversion = "3.5";
-        public const string pyver = "35";
+        internal const string _pyversion = "3.5";
+        internal const string _pyver = "35";
 #elif PYTHON36
-        public const string pyversion = "3.6";
-        public const string pyver = "36";
-#elif PYTHON37 // TODO: Add `interop37.cs` after PY37 is released
-        public const string pyversion = "3.7";
-        public const string pyver = "37";
+        internal const string _pyversion = "3.6";
+        internal const string _pyver = "36";
+#elif PYTHON37
+        internal const string _pyversion = "3.7";
+        internal const string _pyver = "37";
 #else
-#error You must define one of PYTHON33 to PYTHON37 or PYTHON27
+#error You must define one of PYTHON34 to PYTHON37 or PYTHON27
 #endif
 
 #if MONO_LINUX || MONO_OSX // Linux/macOS use dotted version string
-        internal const string dllBase = "python" + pyversion;
+        internal const string dllBase = "python" + _pyversion;
 #else // Windows
-        internal const string dllBase = "python" + pyver;
+        internal const string dllBase = "python" + _pyver;
 #endif
 
 #if PYTHON_WITH_PYDEBUG
@@ -139,35 +173,107 @@ public class Runtime
         internal const string dllWithPyMalloc = "";
 #endif
 
-#if PYTHON_WITHOUT_ENABLE_SHARED
-        public const string PythonDll = "__Internal";
+        // C# compiler copies constants to the assemblies that references this library.
+        // We needs to replace all public constants to static readonly fields to allow 
+        // binary substitution of different Python.Runtime.dll builds in a target application.
+
+        public static readonly string PythonDLL = _PythonDll;
+
+#if PYTHON_WITHOUT_ENABLE_SHARED && !NETSTANDARD
+        internal const string _PythonDll = "__Internal";
 #else
-        public const string PythonDll = dllBase + dllWithPyDebug + dllWithPyMalloc;
+        internal const string _PythonDll = dllBase + dllWithPyDebug + dllWithPyMalloc;
 #endif
 
-        public static readonly int pyversionnumber = Convert.ToInt32(pyver);
+        public static readonly int pyversionnumber = Convert.ToInt32(_pyver);
 
         // set to true when python is finalizing
         internal static object IsFinalizingLock = new object();
         internal static bool IsFinalizing;
 
         internal static bool Is32Bit = IntPtr.Size == 4;
+
+        // .NET core: System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+        internal static bool IsWindows = Environment.OSVersion.Platform == PlatformID.Win32NT;
+
+        /// <summary>
+        /// Operating system type as reported by Python.
+        /// </summary>
+        public enum OperatingSystemType
+        {
+            Windows,
+            Darwin,
+            Linux,
+            Other
+        }
+
+        static readonly Dictionary<string, OperatingSystemType> OperatingSystemTypeMapping = new Dictionary<string, OperatingSystemType>()
+        {
+            { "Windows", OperatingSystemType.Windows },
+            { "Darwin", OperatingSystemType.Darwin },
+            { "Linux", OperatingSystemType.Linux },
+        };
+
+        /// <summary>
+        /// Gets the operating system as reported by python's platform.system().
+        /// </summary>
+        public static OperatingSystemType OperatingSystem { get; private set; }
+
+        /// <summary>
+        /// Gets the operating system as reported by python's platform.system().
+        /// </summary>
+        public static string OperatingSystemName { get; private set; }
+
+        public enum MachineType
+        {
+            i386,
+            x86_64,
+            Other
+        };
+
+        /// <summary>
+        /// Map lower-case version of the python machine name to the processor
+        /// type. There are aliases, e.g. x86_64 and amd64 are two names for
+        /// the same thing. Make sure to lower-case the search string, because
+        /// capitalization can differ.
+        /// </summary>
+        static readonly Dictionary<string, MachineType> MachineTypeMapping = new Dictionary<string, MachineType>()
+        {
+            ["i386"] = MachineType.i386,
+            ["i686"] = MachineType.i386,
+            ["x86"] = MachineType.i386,
+            ["x86_64"] = MachineType.x86_64,
+            ["amd64"] = MachineType.x86_64,
+            ["x64"] = MachineType.x86_64,
+            ["em64t"] = MachineType.x86_64,
+        };
+
+        /// <summary>
+        /// Gets the machine architecture as reported by python's platform.machine().
+        /// </summary>
+        public static MachineType Machine { get; private set; }/* set in Initialize using python's platform.machine */
+
+        /// <summary>
+        /// Gets the machine architecture as reported by python's platform.machine().
+        /// </summary>
+        public static string MachineName { get; private set; }
+
         internal static bool IsPython2 = pyversionnumber < 30;
         internal static bool IsPython3 = pyversionnumber >= 30;
 
         /// <summary>
         /// Encoding to use to convert Unicode to/from Managed to Native
         /// </summary>
-        internal static readonly Encoding PyEncoding = UCS == 2 ? Encoding.Unicode : Encoding.UTF32;
+        internal static readonly Encoding PyEncoding = _UCS == 2 ? Encoding.Unicode : Encoding.UTF32;
 
         /// <summary>
         /// Initialize the runtime...
         /// </summary>
-        internal static void Initialize()
+        internal static void Initialize(bool initSigs = false)
         {
             if (Py_IsInitialized() == 0)
             {
-                Py_Initialize();
+                Py_InitializeEx(initSigs ? 1 : 0);
             }
 
             if (PyEval_ThreadsInitialized() == 0)
@@ -175,6 +281,15 @@ internal static void Initialize()
                 PyEval_InitThreads();
             }
 
+            IsFinalizing = false;
+
+            CLRModule.Reset();
+            GenericUtil.Reset();
+            PyScopeManager.Reset();
+            ClassManager.Reset();
+            ClassDerivedObject.Reset();
+            TypeManager.Reset();
+
             IntPtr op;
             IntPtr dict;
             if (IsPython3)
@@ -274,20 +389,24 @@ internal static void Initialize()
 
             Error = new IntPtr(-1);
 
-#if PYTHON3
             IntPtr dllLocal = IntPtr.Zero;
-            if (PythonDll != "__Internal")
+
+            if (_PythonDll != "__Internal")
             {
-                NativeMethods.LoadLibrary(PythonDll);
+                dllLocal = NativeMethods.LoadLibrary(_PythonDll);
             }
             _PyObject_NextNotImplemented = NativeMethods.GetProcAddress(dllLocal, "_PyObject_NextNotImplemented");
+
 #if !(MONO_LINUX || MONO_OSX)
             if (dllLocal != IntPtr.Zero)
             {
                 NativeMethods.FreeLibrary(dllLocal);
             }
 #endif
-#endif
+            // Initialize data about the platform we're running on. We need
+            // this for the type manager and potentially other details. Must
+            // happen after caching the python types, above.
+            InitializePlatformData();
 
             // Initialize modules that depend on the runtime class.
             AssemblyManager.Initialize();
@@ -305,6 +424,53 @@ internal static void Initialize()
             AssemblyManager.UpdatePath();
         }
 
+        /// <summary>
+        /// Initializes the data about platforms.
+        ///
+        /// This must be the last step when initializing the runtime:
+        /// GetManagedString needs to have the cached values for types.
+        /// But it must run before initializing anything outside the runtime
+        /// because those rely on the platform data.
+        /// </summary>
+        private static void InitializePlatformData()
+        {
+            IntPtr op;
+            IntPtr fn;
+            IntPtr platformModule = PyImport_ImportModule("platform");
+            IntPtr emptyTuple = PyTuple_New(0);
+
+            fn = PyObject_GetAttrString(platformModule, "system");
+            op = PyObject_Call(fn, emptyTuple, IntPtr.Zero);
+            OperatingSystemName = GetManagedString(op);
+            XDecref(op);
+            XDecref(fn);
+
+            fn = PyObject_GetAttrString(platformModule, "machine");
+            op = PyObject_Call(fn, emptyTuple, IntPtr.Zero);
+            MachineName = GetManagedString(op);
+            XDecref(op);
+            XDecref(fn);
+
+            XDecref(emptyTuple);
+            XDecref(platformModule);
+
+            // Now convert the strings into enum values so we can do switch
+            // statements rather than constant parsing.
+            OperatingSystemType OSType;
+            if (!OperatingSystemTypeMapping.TryGetValue(OperatingSystemName, out OSType))
+            {
+                OSType = OperatingSystemType.Other;
+            }
+            OperatingSystem = OSType;
+
+            MachineType MType;
+            if (!MachineTypeMapping.TryGetValue(MachineName.ToLower(), out MType))
+            {
+                MType = MachineType.Other;
+            }
+            Machine = MType;
+        }
+
         internal static void Shutdown()
         {
             AssemblyManager.Shutdown();
@@ -349,8 +515,8 @@ internal static int AtExit()
 
 #if PYTHON3
         internal static IntPtr PyBytesType;
-        internal static IntPtr _PyObject_NextNotImplemented;
 #endif
+        internal static IntPtr _PyObject_NextNotImplemented;
 
         internal static IntPtr PyNotImplemented;
         internal const int Py_LT = 0;
@@ -374,38 +540,15 @@ internal static int AtExit()
         /// </remarks>
         internal static void CheckExceptionOccurred()
         {
-            if (PyErr_Occurred() != 0)
+            if (PyErr_Occurred() != IntPtr.Zero)
             {
                 throw new PythonException();
             }
         }
 
-        internal static IntPtr GetBoundArgTuple(IntPtr obj, IntPtr args)
-        {
-            if (PyObject_TYPE(args) != PyTupleType)
-            {
-                Exceptions.SetError(Exceptions.TypeError, "tuple expected");
-                return IntPtr.Zero;
-            }
-            int size = PyTuple_Size(args);
-            IntPtr items = PyTuple_New(size + 1);
-            PyTuple_SetItem(items, 0, obj);
-            XIncref(obj);
-
-            for (var i = 0; i < size; i++)
-            {
-                IntPtr item = PyTuple_GetItem(args, i);
-                XIncref(item);
-                PyTuple_SetItem(items, i + 1, item);
-            }
-
-            return items;
-        }
-
-
         internal static IntPtr ExtendTuple(IntPtr t, params IntPtr[] args)
         {
-            int size = PyTuple_Size(t);
+            var size = PyTuple_Size(t);
             int add = args.Length;
             IntPtr item;
 
@@ -448,7 +591,7 @@ internal static Type[] PythonArgsToTypeArray(IntPtr arg, bool mangleObjects)
                 free = true;
             }
 
-            int n = PyTuple_Size(args);
+            var n = PyTuple_Size(args);
             var types = new Type[n];
             Type t = null;
 
@@ -499,7 +642,7 @@ internal static Type[] PythonArgsToTypeArray(IntPtr arg, bool mangleObjects)
         /// </summary>
         internal static unsafe void XIncref(IntPtr op)
         {
-#if PYTHON_WITH_PYDEBUG
+#if PYTHON_WITH_PYDEBUG || NETSTANDARD
             Py_IncRef(op);
             return;
 #else
@@ -520,7 +663,7 @@ internal static unsafe void XIncref(IntPtr op)
 
         internal static unsafe void XDecref(IntPtr op)
         {
-#if PYTHON_WITH_PYDEBUG
+#if PYTHON_WITH_PYDEBUG || NETSTANDARD
             Py_DecRef(op);
             return;
 #else
@@ -570,7 +713,7 @@ internal static unsafe long Refcount(IntPtr op)
         /// Limit this function usage for Testing and Py_Debug builds
         /// </summary>
         /// <param name="ob">PyObject Ptr</param>
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_IncRef(IntPtr ob);
 
         /// <summary>
@@ -578,157 +721,163 @@ internal static unsafe long Refcount(IntPtr op)
         /// Limit this function usage for Testing and Py_Debug builds
         /// </summary>
         /// <param name="ob">PyObject Ptr</param>
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_DecRef(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_Initialize();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern void Py_InitializeEx(int initsigs);
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int Py_IsInitialized();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_Finalize();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_NewInterpreter();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_EndInterpreter(IntPtr threadState);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyThreadState_New(IntPtr istate);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyThreadState_Get();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyThread_get_key_value(IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyThread_get_thread_ident();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyThread_set_key_value(IntPtr key, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyThreadState_Swap(IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyGILState_Ensure();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyGILState_Release(IntPtr gs);
 
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyGILState_GetThisThreadState();
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         public static extern int Py_Main(
             int argc,
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(StrArrayMarshaler))] string[] argv
         );
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         public static extern int Py_Main(int argc, string[] argv);
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_InitThreads();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyEval_ThreadsInitialized();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_AcquireLock();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_ReleaseLock();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_AcquireThread(IntPtr tstate);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_ReleaseThread(IntPtr tstate);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyEval_SaveThread();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyEval_RestoreThread(IntPtr tstate);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyEval_GetBuiltins();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyEval_GetGlobals();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyEval_GetLocals();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetProgramName();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_SetProgramName(IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetPythonHome();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_SetPythonHome(IntPtr home);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetPath();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void Py_SetPath(IntPtr home);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetVersion();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetPlatform();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetCopyright();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetCompiler();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_GetBuildInfo();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyRun_SimpleString(string code);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyRun_String(string code, IntPtr st, IntPtr globals, IntPtr locals);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern IntPtr PyEval_EvalCode(IntPtr co, IntPtr globals, IntPtr locals);
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr Py_CompileString(string code, string file, IntPtr tok);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_ExecCodeModule(string name, IntPtr code);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyCFunction_NewEx(IntPtr ml, IntPtr self, IntPtr mod);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyCFunction_Call(IntPtr func, IntPtr args, IntPtr kw);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyClass_New(IntPtr bases, IntPtr dict, IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyInstance_New(IntPtr cls, IntPtr args, IntPtr kw);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyInstance_NewRaw(IntPtr cls, IntPtr dict);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyMethod_New(IntPtr func, IntPtr self, IntPtr cls);
 
 
@@ -777,44 +926,59 @@ internal static string PyObject_GetTypeName(IntPtr op)
             return Marshal.PtrToStringAnsi(ppName);
         }
 
-        [DllImport(PythonDll)]
+        /// <summary>
+        /// Test whether the Python object is an iterable.
+        /// </summary>
+        internal static bool PyObject_IsIterable(IntPtr pointer)
+        {
+            var ob_type = Marshal.ReadIntPtr(pointer, ObjectOffset.ob_type);
+#if PYTHON2
+            long tp_flags = Util.ReadCLong(ob_type, TypeOffset.tp_flags);
+            if ((tp_flags & TypeFlags.HaveIter) == 0)
+                return false;
+#endif
+            IntPtr tp_iter = Marshal.ReadIntPtr(ob_type, TypeOffset.tp_iter);
+            return tp_iter != IntPtr.Zero;
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_HasAttrString(IntPtr pointer, string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GetAttrString(IntPtr pointer, string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_SetAttrString(IntPtr pointer, string name, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_HasAttr(IntPtr pointer, IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GetAttr(IntPtr pointer, IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_SetAttr(IntPtr pointer, IntPtr name, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GetItem(IntPtr pointer, IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_SetItem(IntPtr pointer, IntPtr key, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_DelItem(IntPtr pointer, IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GetIter(IntPtr op);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_CallObject(IntPtr pointer, IntPtr args);
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_RichCompareBool(IntPtr value1, IntPtr value2, int opid);
 
         internal static int PyObject_Compare(IntPtr value1, IntPtr value2)
@@ -842,46 +1006,52 @@ internal static int PyObject_Compare(IntPtr value1, IntPtr value2)
             return -1;
         }
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_Compare(IntPtr value1, IntPtr value2);
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_IsInstance(IntPtr ob, IntPtr type);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_IsSubclass(IntPtr ob, IntPtr type);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyCallable_Check(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_IsTrue(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_Not(IntPtr pointer);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyObject_Size(IntPtr pointer);
+        internal static long PyObject_Size(IntPtr pointer)
+        {
+            return (long) _PyObject_Size(pointer);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyObject_Size")]
+        private static extern IntPtr _PyObject_Size(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Hash(IntPtr op);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Repr(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Str(IntPtr pointer);
 
 #if PYTHON3
-        [DllImport(PythonDll, EntryPoint = "PyObject_Str")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyObject_Str")]
         internal static extern IntPtr PyObject_Unicode(IntPtr pointer);
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Unicode(IntPtr pointer);
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_Dir(IntPtr pointer);
 
 
@@ -890,20 +1060,21 @@ internal static int PyObject_Compare(IntPtr value1, IntPtr value2)
         //====================================================================
 
 #if PYTHON3
-        [DllImport(PythonDll, EntryPoint = "PyNumber_Long")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyNumber_Long")]
         internal static extern IntPtr PyNumber_Int(IntPtr ob);
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Int(IntPtr ob);
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Long(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Float(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern bool PyNumber_Check(IntPtr ob);
 
         internal static bool PyInt_Check(IntPtr ob)
@@ -929,28 +1100,32 @@ internal static IntPtr PyInt_FromInt64(long value)
         }
 
 #if PYTHON3
-        [DllImport(PythonDll, EntryPoint = "PyLong_FromLong")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyLong_FromLong")]
         private static extern IntPtr PyInt_FromLong(IntPtr value);
 
-        [DllImport(PythonDll, EntryPoint = "PyLong_AsLong")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyLong_AsLong")]
         internal static extern int PyInt_AsLong(IntPtr value);
 
-        [DllImport(PythonDll, EntryPoint = "PyLong_FromString")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyLong_FromString")]
         internal static extern IntPtr PyInt_FromString(string value, IntPtr end, int radix);
 
-        [DllImport(PythonDll, EntryPoint = "PyLong_GetMax")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyLong_GetMax")]
         internal static extern int PyInt_GetMax();
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         private static extern IntPtr PyInt_FromLong(IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyInt_AsLong(IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyInt_FromString(string value, IntPtr end, int radix);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyInt_GetMax();
 #endif
 
@@ -959,34 +1134,34 @@ internal static bool PyLong_Check(IntPtr ob)
             return PyObject_TYPE(ob) == PyLongType;
         }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromLong(long value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromUnsignedLong(uint value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromDouble(double value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromLongLong(long value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromUnsignedLongLong(ulong value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyLong_FromString(string value, IntPtr end, int radix);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyLong_AsLong(IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern uint PyLong_AsUnsignedLong(IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern long PyLong_AsLongLong(IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern ulong PyLong_AsUnsignedLongLong(IntPtr value);
 
         internal static bool PyFloat_Check(IntPtr ob)
@@ -994,88 +1169,88 @@ internal static bool PyFloat_Check(IntPtr ob)
             return PyObject_TYPE(ob) == PyFloatType;
         }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyFloat_FromDouble(double value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyFloat_FromString(IntPtr value, IntPtr junk);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern double PyFloat_AsDouble(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Add(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Subtract(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Multiply(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Divide(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_And(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Xor(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Or(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Lshift(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Rshift(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Power(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Remainder(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceAdd(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceSubtract(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceMultiply(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceDivide(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceAnd(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceXor(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceOr(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceLshift(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceRshift(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlacePower(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_InPlaceRemainder(IntPtr o1, IntPtr o2);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Negative(IntPtr o1);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Positive(IntPtr o1);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyNumber_Invert(IntPtr o1);
 
 
@@ -1083,49 +1258,94 @@ internal static bool PyFloat_Check(IntPtr ob)
         // Python sequence API
         //====================================================================
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern bool PySequence_Check(IntPtr pointer);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PySequence_GetItem(IntPtr pointer, int index);
+        internal static IntPtr PySequence_GetItem(IntPtr pointer, long index)
+        {
+            return PySequence_GetItem(pointer, new IntPtr(index));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PySequence_GetItem(IntPtr pointer, IntPtr index);
+
+        internal static int PySequence_SetItem(IntPtr pointer, long index, IntPtr value)
+        {
+            return PySequence_SetItem(pointer, new IntPtr(index), value);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PySequence_SetItem(IntPtr pointer, IntPtr index, IntPtr value);
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_SetItem(IntPtr pointer, int index, IntPtr value);
+        internal static int PySequence_DelItem(IntPtr pointer, long index)
+        {
+            return PySequence_DelItem(pointer, new IntPtr(index));
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_DelItem(IntPtr pointer, int index);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PySequence_DelItem(IntPtr pointer, IntPtr index);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PySequence_GetSlice(IntPtr pointer, int i1, int i2);
+        internal static IntPtr PySequence_GetSlice(IntPtr pointer, long i1, long i2)
+        {
+            return PySequence_GetSlice(pointer, new IntPtr(i1), new IntPtr(i2));
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_SetSlice(IntPtr pointer, int i1, int i2, IntPtr v);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PySequence_GetSlice(IntPtr pointer, IntPtr i1, IntPtr i2);
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_DelSlice(IntPtr pointer, int i1, int i2);
+        internal static int PySequence_SetSlice(IntPtr pointer, long i1, long i2, IntPtr v)
+        {
+            return PySequence_SetSlice(pointer, new IntPtr(i1), new IntPtr(i2), v);
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_Size(IntPtr pointer);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PySequence_SetSlice(IntPtr pointer, IntPtr i1, IntPtr i2, IntPtr v);
 
-        [DllImport(PythonDll)]
+        internal static int PySequence_DelSlice(IntPtr pointer, long i1, long i2)
+        {
+            return PySequence_DelSlice(pointer, new IntPtr(i1), new IntPtr(i2));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PySequence_DelSlice(IntPtr pointer, IntPtr i1, IntPtr i2);
+
+        internal static long PySequence_Size(IntPtr pointer)
+        {
+            return (long) _PySequence_Size(pointer);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PySequence_Size")]
+        private static extern IntPtr _PySequence_Size(IntPtr pointer);
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PySequence_Contains(IntPtr pointer, IntPtr item);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PySequence_Concat(IntPtr pointer, IntPtr other);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PySequence_Repeat(IntPtr pointer, int count);
+        internal static IntPtr PySequence_Repeat(IntPtr pointer, long count)
+        {
+            return PySequence_Repeat(pointer, new IntPtr(count));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PySequence_Repeat(IntPtr pointer, IntPtr count);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PySequence_Index(IntPtr pointer, IntPtr item);
 
-        [DllImport(PythonDll)]
-        internal static extern int PySequence_Count(IntPtr pointer, IntPtr value);
+        internal static long PySequence_Count(IntPtr pointer, IntPtr value)
+        {
+            return (long) _PySequence_Count(pointer, value);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PySequence_Count")]
+        private static extern IntPtr _PySequence_Count(IntPtr pointer, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PySequence_Tuple(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PySequence_List(IntPtr pointer);
 
 
@@ -1146,37 +1366,62 @@ internal static bool PyString_Check(IntPtr ob)
 
         internal static IntPtr PyString_FromString(string value)
         {
+#if PYTHON3
+            return PyUnicode_FromKindAndData(_UCS, value, value.Length);
+#elif PYTHON2
             return PyString_FromStringAndSize(value, value.Length);
+#endif
         }
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyBytes_FromString(string op);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyBytes_Size(IntPtr op);
+        internal static long PyBytes_Size(IntPtr op)
+        {
+            return (long) _PyBytes_Size(op);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyBytes_Size")]
+        private static extern IntPtr _PyBytes_Size(IntPtr op);
 
         internal static IntPtr PyBytes_AS_STRING(IntPtr ob)
         {
             return ob + BytesOffset.ob_sval;
         }
 
-        [DllImport(PythonDll, EntryPoint = "PyUnicode_FromStringAndSize")]
-        internal static extern IntPtr PyString_FromStringAndSize(
+        internal static IntPtr PyString_FromStringAndSize(string value, long size)
+        {
+            return _PyString_FromStringAndSize(value, new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = "PyUnicode_FromStringAndSize")]
+        internal static extern IntPtr _PyString_FromStringAndSize(
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string value,
-            int size
+            IntPtr size
         );
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyUnicode_FromStringAndSize(IntPtr value, int size);
+        internal static IntPtr PyUnicode_FromStringAndSize(IntPtr value, long size)
+        {
+            return PyUnicode_FromStringAndSize(value, new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyUnicode_FromStringAndSize(IntPtr value, IntPtr size);
 #elif PYTHON2
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyString_FromStringAndSize(string value, int size);
+        internal static IntPtr PyString_FromStringAndSize(string value, long size)
+        {
+            return PyString_FromStringAndSize(value, new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyString_FromStringAndSize(string value, IntPtr size);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyString_AsString(IntPtr op);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyString_Size(IntPtr pointer);
 #endif
 
@@ -1186,52 +1431,78 @@ internal static bool PyUnicode_Check(IntPtr ob)
         }
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyUnicode_FromObject(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyUnicode_FromEncodedObject(IntPtr ob, IntPtr enc, IntPtr err);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyUnicode_FromKindAndData(
+        internal static IntPtr PyUnicode_FromKindAndData(int kind, string s, long size)
+        {
+            return PyUnicode_FromKindAndData(kind, s, new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyUnicode_FromKindAndData(
             int kind,
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UcsMarshaler))] string s,
-            int size
+            IntPtr size
         );
 
-        internal static IntPtr PyUnicode_FromUnicode(string s, int size)
+        internal static IntPtr PyUnicode_FromUnicode(string s, long size)
         {
-            return PyUnicode_FromKindAndData(UCS, s, size);
+            return PyUnicode_FromKindAndData(_UCS, s, size);
         }
 
-        [DllImport(PythonDll)]
-        internal static extern int PyUnicode_GetSize(IntPtr ob);
+        internal static long PyUnicode_GetSize(IntPtr ob)
+        {
+            return (long)_PyUnicode_GetSize(ob);
+        }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyUnicode_GetSize")]
+        private static extern IntPtr _PyUnicode_GetSize(IntPtr ob);
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyUnicode_AsUnicode(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyUnicode_FromOrdinal(int c);
 #elif PYTHON2
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "FromObject")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "FromObject")]
         internal static extern IntPtr PyUnicode_FromObject(IntPtr ob);
 
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "FromEncodedObject")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "FromEncodedObject")]
         internal static extern IntPtr PyUnicode_FromEncodedObject(IntPtr ob, IntPtr enc, IntPtr err);
 
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "FromUnicode")]
-        internal static extern IntPtr PyUnicode_FromUnicode(
+        internal static IntPtr PyUnicode_FromUnicode(string s, long size)
+        {
+            return PyUnicode_FromUnicode(s, new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "FromUnicode")]
+        private static extern IntPtr PyUnicode_FromUnicode(
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UcsMarshaler))] string s,
-            int size
+            IntPtr size
         );
 
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "GetSize")]
-        internal static extern int PyUnicode_GetSize(IntPtr ob);
+        internal static long PyUnicode_GetSize(IntPtr ob)
+        {
+            return (long) _PyUnicode_GetSize(ob);
+        }
 
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "AsUnicode")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "GetSize")]
+        internal static extern IntPtr _PyUnicode_GetSize(IntPtr ob);
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "AsUnicode")]
         internal static extern IntPtr PyUnicode_AsUnicode(IntPtr ob);
 
-        [DllImport(PythonDll, EntryPoint = PyUnicodeEntryPoint + "FromOrdinal")]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl,
+            EntryPoint = PyUnicodeEntryPoint + "FromOrdinal")]
         internal static extern IntPtr PyUnicode_FromOrdinal(int c);
 #endif
 
@@ -1267,9 +1538,9 @@ internal static string GetManagedString(IntPtr op)
             if (type == PyUnicodeType)
             {
                 IntPtr p = PyUnicode_AsUnicode(op);
-                int length = PyUnicode_GetSize(op);
+                int length = (int)PyUnicode_GetSize(op);
 
-                int size = length * UCS;
+                int size = length * _UCS;
                 var buffer = new byte[size];
                 Marshal.Copy(p, buffer, 0, size);
                 return PyEncoding.GetString(buffer, 0, size);
@@ -1288,53 +1559,58 @@ internal static bool PyDict_Check(IntPtr ob)
             return PyObject_TYPE(ob) == PyDictType;
         }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_New();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDictProxy_New(IntPtr dict);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_GetItem(IntPtr pointer, IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_GetItemString(IntPtr pointer, string key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyDict_SetItem(IntPtr pointer, IntPtr key, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyDict_SetItemString(IntPtr pointer, string key, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyDict_DelItem(IntPtr pointer, IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyDict_DelItemString(IntPtr pointer, string key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyMapping_HasKey(IntPtr pointer, IntPtr key);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_Keys(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_Values(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_Items(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyDict_Copy(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyDict_Update(IntPtr pointer, IntPtr other);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyDict_Clear(IntPtr pointer);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyDict_Size(IntPtr pointer);
+        internal static long PyDict_Size(IntPtr pointer)
+        {
+            return (long) _PyDict_Size(pointer);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyDict_Size")]
+        internal static extern IntPtr _PyDict_Size(IntPtr pointer);
 
 
         //====================================================================
@@ -1346,39 +1622,73 @@ internal static bool PyList_Check(IntPtr ob)
             return PyObject_TYPE(ob) == PyListType;
         }
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyList_New(int size);
+        internal static IntPtr PyList_New(long size)
+        {
+            return PyList_New(new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyList_New(IntPtr size);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyList_AsTuple(IntPtr pointer);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyList_GetItem(IntPtr pointer, int index);
+        internal static IntPtr PyList_GetItem(IntPtr pointer, long index)
+        {
+            return PyList_GetItem(pointer, new IntPtr(index));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyList_GetItem(IntPtr pointer, IntPtr index);
+
+        internal static int PyList_SetItem(IntPtr pointer, long index, IntPtr value)
+        {
+            return PyList_SetItem(pointer, new IntPtr(index), value);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PyList_SetItem(IntPtr pointer, IntPtr index, IntPtr value);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyList_SetItem(IntPtr pointer, int index, IntPtr value);
+        internal static int PyList_Insert(IntPtr pointer, long index, IntPtr value)
+        {
+            return PyList_Insert(pointer, new IntPtr(index), value);
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PyList_Insert(IntPtr pointer, int index, IntPtr value);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PyList_Insert(IntPtr pointer, IntPtr index, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyList_Append(IntPtr pointer, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyList_Reverse(IntPtr pointer);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyList_Sort(IntPtr pointer);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyList_GetSlice(IntPtr pointer, int start, int end);
+        internal static IntPtr PyList_GetSlice(IntPtr pointer, long start, long end)
+        {
+            return PyList_GetSlice(pointer, new IntPtr(start), new IntPtr(end));
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PyList_SetSlice(IntPtr pointer, int start, int end, IntPtr value);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyList_GetSlice(IntPtr pointer, IntPtr start, IntPtr end);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyList_Size(IntPtr pointer);
+        internal static int PyList_SetSlice(IntPtr pointer, long start, long end, IntPtr value)
+        {
+            return PyList_SetSlice(pointer, new IntPtr(start), new IntPtr(end), value);
+        }
 
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PyList_SetSlice(IntPtr pointer, IntPtr start, IntPtr end, IntPtr value);
+
+        internal static long PyList_Size(IntPtr pointer)
+        {
+            return (long) _PyList_Size(pointer);
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyList_Size")]
+        private static extern IntPtr _PyList_Size(IntPtr pointer);
 
         //====================================================================
         // Python tuple API
@@ -1389,39 +1699,64 @@ internal static bool PyTuple_Check(IntPtr ob)
             return PyObject_TYPE(ob) == PyTupleType;
         }
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyTuple_New(int size);
+        internal static IntPtr PyTuple_New(long size)
+        {
+            return PyTuple_New(new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyTuple_New(IntPtr size);
+
+        internal static IntPtr PyTuple_GetItem(IntPtr pointer, long index)
+        {
+            return PyTuple_GetItem(pointer, new IntPtr(index));
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyTuple_GetItem(IntPtr pointer, int index);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyTuple_GetItem(IntPtr pointer, IntPtr index);
+
+        internal static int PyTuple_SetItem(IntPtr pointer, long index, IntPtr value)
+        {
+            return PyTuple_SetItem(pointer, new IntPtr(index), value);
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PyTuple_SetItem(IntPtr pointer, int index, IntPtr value);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern int PyTuple_SetItem(IntPtr pointer, IntPtr index, IntPtr value);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyTuple_GetSlice(IntPtr pointer, int start, int end);
+        internal static IntPtr PyTuple_GetSlice(IntPtr pointer, long start, long end)
+        {
+            return PyTuple_GetSlice(pointer, new IntPtr(start), new IntPtr(end));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyTuple_GetSlice(IntPtr pointer, IntPtr start, IntPtr end);
+
+        internal static long PyTuple_Size(IntPtr pointer)
+        {
+            return (long) _PyTuple_Size(pointer);
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern int PyTuple_Size(IntPtr pointer);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl, EntryPoint = "PyTuple_Size")]
+        private static extern IntPtr _PyTuple_Size(IntPtr pointer);
 
 
         //====================================================================
         // Python iterator API
         //====================================================================
 
-#if PYTHON2
-        [DllImport(PythonDll)]
-        internal static extern bool PyIter_Check(IntPtr pointer);
-#elif PYTHON3
         internal static bool PyIter_Check(IntPtr pointer)
         {
-            var ob_type = (IntPtr)Marshal.PtrToStructure(pointer + ObjectOffset.ob_type, typeof(IntPtr));
-            IntPtr tp_iternext = ob_type + TypeOffset.tp_iternext;
-            return tp_iternext != null && tp_iternext != _PyObject_NextNotImplemented;
-        }
+            var ob_type = Marshal.ReadIntPtr(pointer, ObjectOffset.ob_type);
+#if PYTHON2
+            long tp_flags = Util.ReadCLong(ob_type, TypeOffset.tp_flags);
+            if ((tp_flags & TypeFlags.HaveIter) == 0)
+                return false;
 #endif
+            IntPtr tp_iternext = Marshal.ReadIntPtr(ob_type, TypeOffset.tp_iternext);
+            return tp_iternext != IntPtr.Zero && tp_iternext != _PyObject_NextNotImplemented;
+        }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyIter_Next(IntPtr pointer);
 
 
@@ -1429,47 +1764,47 @@ internal static bool PyIter_Check(IntPtr pointer)
         // Python module API
         //====================================================================
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyModule_New(string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern string PyModule_GetName(IntPtr module);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyModule_GetDict(IntPtr module);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern string PyModule_GetFilename(IntPtr module);
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyModule_Create2(IntPtr module, int apiver);
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_Import(IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_ImportModule(string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_ReloadModule(IntPtr module);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_AddModule(string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyImport_GetModuleDict();
 
 #if PYTHON3
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PySys_SetArgvEx(
             int argc,
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(StrArrayMarshaler))] string[] argv,
             int updatepath
         );
 #elif PYTHON2
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PySys_SetArgvEx(
             int argc,
             string[] argv,
@@ -1477,10 +1812,10 @@ int updatepath
         );
 #endif
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PySys_GetObject(string name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PySys_SetObject(string name, IntPtr ob);
 
 
@@ -1493,10 +1828,10 @@ internal static bool PyType_Check(IntPtr ob)
             return PyObject_TypeCheck(ob, PyTypeType);
         }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyType_Modified(IntPtr type);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern bool PyType_IsSubtype(IntPtr t1, IntPtr t2);
 
         internal static bool PyObject_TypeCheck(IntPtr ob, IntPtr tp)
@@ -1505,37 +1840,42 @@ internal static bool PyObject_TypeCheck(IntPtr ob, IntPtr tp)
             return (t == tp) || PyType_IsSubtype(t, tp);
         }
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyType_GenericNew(IntPtr type, IntPtr args, IntPtr kw);
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyType_GenericAlloc(IntPtr type, int n);
+        internal static IntPtr PyType_GenericAlloc(IntPtr type, long n)
+        {
+            return PyType_GenericAlloc(type, new IntPtr(n));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyType_GenericAlloc(IntPtr type, IntPtr n);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyType_Ready(IntPtr type);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr _PyType_Lookup(IntPtr type, IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GenericGetAttr(IntPtr obj, IntPtr name);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyObject_GenericSetAttr(IntPtr obj, IntPtr name, IntPtr value);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr _PyObject_GetDictPtr(IntPtr obj);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyObject_GC_New(IntPtr tp);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyObject_GC_Del(IntPtr tp);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyObject_GC_Track(IntPtr tp);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyObject_GC_UnTrack(IntPtr tp);
 
 
@@ -1543,13 +1883,23 @@ internal static bool PyObject_TypeCheck(IntPtr ob, IntPtr tp)
         // Python memory API
         //====================================================================
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyMem_Malloc(int size);
+        internal static IntPtr PyMem_Malloc(long size)
+        {
+            return PyMem_Malloc(new IntPtr(size));
+        }
+
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyMem_Malloc(IntPtr size);
+
+        internal static IntPtr PyMem_Realloc(IntPtr ptr, long size)
+        {
+            return PyMem_Realloc(ptr, new IntPtr(size));
+        }
 
-        [DllImport(PythonDll)]
-        internal static extern IntPtr PyMem_Realloc(IntPtr ptr, int size);
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr PyMem_Realloc(IntPtr ptr, IntPtr size);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyMem_Free(IntPtr ptr);
 
 
@@ -1557,40 +1907,40 @@ internal static bool PyObject_TypeCheck(IntPtr ob, IntPtr tp)
         // Python exception API
         //====================================================================
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_SetString(IntPtr ob, string message);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_SetObject(IntPtr ob, IntPtr message);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyErr_SetFromErrno(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_SetNone(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyErr_ExceptionMatches(IntPtr exception);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int PyErr_GivenExceptionMatches(IntPtr ob, IntPtr val);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_NormalizeException(IntPtr ob, IntPtr val, IntPtr tb);
 
-        [DllImport(PythonDll)]
-        internal static extern int PyErr_Occurred();
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern IntPtr PyErr_Occurred();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_Fetch(ref IntPtr ob, ref IntPtr val, ref IntPtr tb);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_Restore(IntPtr ob, IntPtr val, IntPtr tb);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_Clear();
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void PyErr_Print();
 
 
@@ -1598,10 +1948,10 @@ internal static bool PyObject_TypeCheck(IntPtr ob, IntPtr tp)
         // Miscellaneous
         //====================================================================
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyMethod_Self(IntPtr ob);
 
-        [DllImport(PythonDll)]
+        [DllImport(_PythonDll, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr PyMethod_Function(IntPtr ob);
     }
 }
diff --git a/src/runtime/typemanager.cs b/src/runtime/typemanager.cs
index 6f373f036..d19c8737f 100644
--- a/src/runtime/typemanager.cs
+++ b/src/runtime/typemanager.cs
@@ -21,6 +21,10 @@ static TypeManager()
             cache = new Dictionary<Type, IntPtr>(128);
         }
 
+        public static void Reset()
+        {
+            cache = new Dictionary<Type, IntPtr>(128);
+        }
 
         /// <summary>
         /// Given a managed Type derived from ExtensionType, get the handle to
@@ -86,7 +90,7 @@ internal static IntPtr CreateType(Type impl)
 
             int flags = TypeFlags.Default | TypeFlags.Managed |
                         TypeFlags.HeapType | TypeFlags.HaveGC;
-            Marshal.WriteIntPtr(type, TypeOffset.tp_flags, (IntPtr)flags);
+            Util.WriteCLong(type, TypeOffset.tp_flags, flags);
 
             Runtime.PyType_Ready(type);
 
@@ -160,7 +164,7 @@ internal static IntPtr CreateType(ManagedType impl, Type clrType)
             flags |= TypeFlags.HeapType;
             flags |= TypeFlags.BaseType;
             flags |= TypeFlags.HaveGC;
-            Marshal.WriteIntPtr(type, TypeOffset.tp_flags, (IntPtr)flags);
+            Util.WriteCLong(type, TypeOffset.tp_flags, flags);
 
             // Leverage followup initialization from the Python runtime. Note
             // that the type of the new type must PyType_Type at the time we
@@ -206,6 +210,7 @@ internal static IntPtr CreateSubType(IntPtr py_name, IntPtr py_base_type, IntPtr
                 if (0 != Runtime.PyMapping_HasKey(py_dict, assemblyKey.Handle))
                 {
                     var pyAssembly = new PyObject(Runtime.PyDict_GetItem(py_dict, assemblyKey.Handle));
+                    Runtime.XIncref(pyAssembly.Handle);
                     disposeList.Add(pyAssembly);
                     if (!Converter.ToManagedValue(pyAssembly.Handle, typeof(string), out assembly, false))
                     {
@@ -218,6 +223,7 @@ internal static IntPtr CreateSubType(IntPtr py_name, IntPtr py_base_type, IntPtr
                 if (0 != Runtime.PyMapping_HasKey(py_dict, namespaceKey.Handle))
                 {
                     var pyNamespace = new PyObject(Runtime.PyDict_GetItem(py_dict, namespaceKey.Handle));
+                    Runtime.XIncref(pyNamespace.Handle);
                     disposeList.Add(pyNamespace);
                     if (!Converter.ToManagedValue(pyNamespace.Handle, typeof(string), out namespaceStr, false))
                     {
@@ -321,7 +327,7 @@ internal static IntPtr CreateMetaType(Type impl)
             flags |= TypeFlags.Managed;
             flags |= TypeFlags.HeapType;
             flags |= TypeFlags.HaveGC;
-            Marshal.WriteIntPtr(type, TypeOffset.tp_flags, (IntPtr)flags);
+            Util.WriteCLong(type, TypeOffset.tp_flags, flags);
 
             // We need space for 3 PyMethodDef structs, each of them
             // 4 int-ptrs in size.
@@ -378,7 +384,7 @@ internal static IntPtr BasicSubType(string name, IntPtr base_, Type impl)
             flags |= TypeFlags.Managed;
             flags |= TypeFlags.HeapType;
             flags |= TypeFlags.HaveGC;
-            Marshal.WriteIntPtr(type, TypeOffset.tp_flags, (IntPtr)flags);
+            Util.WriteCLong(type, TypeOffset.tp_flags, flags);
 
             CopySlot(base_, type, TypeOffset.tp_traverse);
             CopySlot(base_, type, TypeOffset.tp_clear);
@@ -445,6 +451,225 @@ internal static IntPtr AllocateTypeObject(string name)
         }
 
 
+        #region Native Code Page
+        /// <summary>
+        /// Initialized by InitializeNativeCodePage.
+        ///
+        /// This points to a page of memory allocated using mmap or VirtualAlloc
+        /// (depending on the system), and marked read and execute (not write).
+        /// Very much on purpose, the page is *not* released on a shutdown and
+        /// is instead leaked. See the TestDomainReload test case.
+        ///
+        /// The contents of the page are two native functions: one that returns 0,
+        /// one that returns 1.
+        ///
+        /// If python didn't keep its gc list through a Py_Finalize we could remove
+        /// this entire section.
+        /// </summary>
+        internal static IntPtr NativeCodePage = IntPtr.Zero;
+
+        /// <summary>
+        /// Structure to describe native code.
+        ///
+        /// Use NativeCode.Active to get the native code for the current platform.
+        ///
+        /// Generate the code by creating the following C code:
+        /// <code>
+        /// int Return0() { return 0; }
+        /// int Return1() { return 1; }
+        /// </code>
+        /// Then compiling on the target platform, e.g. with gcc or clang:
+        /// <code>cc -c -fomit-frame-pointer -O2 foo.c</code>
+        /// And then analyzing the resulting functions with a hex editor, e.g.:
+        /// <code>objdump -disassemble foo.o</code>
+        /// </summary>
+        internal class NativeCode
+        {
+            /// <summary>
+            /// The code, as a string of bytes.
+            /// </summary>
+            public byte[] Code { get; private set; }
+
+            /// <summary>
+            /// Where does the "return 0" function start?
+            /// </summary>
+            public int Return0 { get; private set; }
+
+            /// <summary>
+            /// Where does the "return 1" function start?
+            /// </summary>
+            public int Return1 { get; private set; }
+
+            public static NativeCode Active
+            {
+                get
+                {
+                    switch(Runtime.Machine)
+                    {
+                        case Runtime.MachineType.i386:
+                            return I386;
+                        case Runtime.MachineType.x86_64:
+                            return X86_64;
+                        default:
+                            throw new NotImplementedException($"No support for {Runtime.MachineName}");
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Code for x86_64. See the class comment for how it was generated.
+            /// </summary>
+            public static readonly NativeCode X86_64 = new NativeCode()
+            {
+                Return0 = 0x10,
+                Return1 = 0,
+                Code = new byte[]
+                {
+                    // First Return1:
+                    0xb8, 0x01, 0x00, 0x00, 0x00, // movl $1, %eax
+                    0xc3, // ret
+
+                    // Now some padding so that Return0 can be 16-byte-aligned.
+                    // I put Return1 first so there's not as much padding to type in.
+                    0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00, // nop
+
+                    // Now Return0.
+                    0x31, 0xc0, // xorl %eax, %eax
+                    0xc3, // ret
+                }
+            };
+
+            /// <summary>
+            /// Code for X86.
+            ///
+            /// It's bitwise identical to X86_64, so we just point to it.
+            /// <see cref="NativeCode.X86_64"/>
+            /// </summary>
+            public static readonly NativeCode I386 = X86_64;
+        }
+
+        /// <summary>
+        /// Platform-dependent mmap and mprotect.
+        /// </summary>
+        internal interface IMemoryMapper
+        {
+            /// <summary>
+            /// Map at least numBytes of memory. Mark the page read-write (but not exec).
+            /// </summary>
+            IntPtr MapWriteable(int numBytes);
+
+            /// <summary>
+            /// Sets the mapped memory to be read-exec (but not write).
+            /// </summary>
+            void SetReadExec(IntPtr mappedMemory, int numBytes);
+        }
+
+        class WindowsMemoryMapper : IMemoryMapper
+        {
+            const UInt32 MEM_COMMIT = 0x1000;
+            const UInt32 MEM_RESERVE = 0x2000;
+            const UInt32 PAGE_READWRITE = 0x04;
+            const UInt32 PAGE_EXECUTE_READ = 0x20;
+
+            [DllImport("kernel32.dll")]
+            static extern IntPtr VirtualAlloc(IntPtr lpAddress, IntPtr dwSize, UInt32 flAllocationType, UInt32 flProtect);
+
+            [DllImport("kernel32.dll")]
+            static extern bool VirtualProtect(IntPtr lpAddress, IntPtr dwSize, UInt32 flNewProtect, out UInt32 lpflOldProtect);
+
+            public IntPtr MapWriteable(int numBytes)
+            {
+                return VirtualAlloc(IntPtr.Zero, new IntPtr(numBytes),
+                                    MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+            }
+
+            public void SetReadExec(IntPtr mappedMemory, int numBytes)
+            {
+                UInt32 _;
+                VirtualProtect(mappedMemory, new IntPtr(numBytes), PAGE_EXECUTE_READ, out _);
+            }
+        }
+
+        class UnixMemoryMapper : IMemoryMapper
+        {
+            const int PROT_READ = 0x1;
+            const int PROT_WRITE = 0x2;
+            const int PROT_EXEC = 0x4;
+
+            const int MAP_PRIVATE = 0x2;
+            int MAP_ANONYMOUS
+            {
+                get
+                {
+                    switch (Runtime.OperatingSystem)
+                    {
+                        case Runtime.OperatingSystemType.Darwin:
+                            return 0x1000;
+                        case Runtime.OperatingSystemType.Linux:
+                            return 0x20;
+                        default:
+                            throw new NotImplementedException($"mmap is not supported on {Runtime.OperatingSystemName}");
+                    }
+                }
+            }
+
+            [DllImport("libc")]
+            static extern IntPtr mmap(IntPtr addr, IntPtr len, int prot, int flags, int fd, IntPtr offset);
+
+            [DllImport("libc")]
+            static extern int mprotect(IntPtr addr, IntPtr len, int prot);
+
+            public IntPtr MapWriteable(int numBytes)
+            {
+                // MAP_PRIVATE must be set on linux, even though MAP_ANON implies it.
+                // It doesn't hurt on darwin, so just do it.
+                return mmap(IntPtr.Zero, new IntPtr(numBytes), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, IntPtr.Zero);
+            }
+
+            public void SetReadExec(IntPtr mappedMemory, int numBytes)
+            {
+                mprotect(mappedMemory, new IntPtr(numBytes), PROT_READ | PROT_EXEC);
+            }
+        }
+
+        internal static IMemoryMapper CreateMemoryMapper()
+        {
+            switch (Runtime.OperatingSystem)
+            {
+                case Runtime.OperatingSystemType.Darwin:
+                case Runtime.OperatingSystemType.Linux:
+                    return new UnixMemoryMapper();
+                case Runtime.OperatingSystemType.Windows:
+                    return new WindowsMemoryMapper();
+                default:
+                    throw new NotImplementedException($"No support for {Runtime.OperatingSystemName}");
+            }
+        }
+
+        /// <summary>
+        /// Initializes the native code page.
+        ///
+        /// Safe to call if we already initialized (this function is idempotent).
+        /// <see cref="NativeCodePage"/>
+        /// </summary>
+        internal static void InitializeNativeCodePage()
+        {
+            // Do nothing if we already initialized.
+            if (NativeCodePage != IntPtr.Zero)
+            {
+                return;
+            }
+
+            // Allocate the page, write the native code into it, then set it
+            // to be executable.
+            IMemoryMapper mapper = CreateMemoryMapper();
+            int codeLength = NativeCode.Active.Code.Length;
+            NativeCodePage = mapper.MapWriteable(codeLength);
+            Marshal.Copy(NativeCode.Active.Code, 0, NativeCodePage, codeLength);
+            mapper.SetReadExec(NativeCodePage, codeLength);
+        }
+#endregion
+
         /// <summary>
         /// Given a newly allocated Python type object and a managed Type that
         /// provides the implementation for the type, connect the type slots of
@@ -452,8 +677,10 @@ internal static IntPtr AllocateTypeObject(string name)
         /// </summary>
         internal static void InitializeSlots(IntPtr type, Type impl)
         {
-            var seen = new Hashtable(8);
-            Type offsetType = typeof(TypeOffset);
+            // We work from the most-derived class up; make sure to get
+            // the most-derived slot and not to override it with a base
+            // class's slot.
+            var seen = new HashSet<string>();
 
             while (impl != null)
             {
@@ -471,24 +698,52 @@ internal static void InitializeSlots(IntPtr type, Type impl)
                         continue;
                     }
 
-                    if (seen[name] != null)
+                    if (seen.Contains(name))
                     {
                         continue;
                     }
 
-                    FieldInfo fi = offsetType.GetField(name);
-                    var offset = (int)fi.GetValue(offsetType);
-
-                    IntPtr slot = Interop.GetThunk(method);
-                    Marshal.WriteIntPtr(type, offset, slot);
+                    InitializeSlot(type, Interop.GetThunk(method), name);
 
-                    seen[name] = 1;
+                    seen.Add(name);
                 }
 
                 impl = impl.BaseType;
             }
+
+            // See the TestDomainReload test: there was a crash related to
+            // the gc-related slots. They always return 0 or 1 because we don't
+            // really support gc:
+            //   tp_traverse (returns 0)
+            //   tp_clear    (returns 0)
+            //   tp_is_gc    (returns 1)
+            // We can't do without: python really wants those slots to exist.
+            // We can't implement those in C# because the application domain
+            // can be shut down and the memory released.
+            InitializeNativeCodePage();
+            InitializeSlot(type, NativeCodePage + NativeCode.Active.Return0, "tp_traverse");
+            InitializeSlot(type, NativeCodePage + NativeCode.Active.Return0, "tp_clear");
+            InitializeSlot(type, NativeCodePage + NativeCode.Active.Return1, "tp_is_gc");
         }
 
+        /// <summary>
+        /// Helper for InitializeSlots.
+        ///
+        /// Initializes one slot to point to a function pointer.
+        /// The function pointer might be a thunk for C#, or it may be
+        /// an address in the NativeCodePage.
+        /// </summary>
+        /// <param name="type">Type being initialized.</param>
+        /// <param name="slot">Function pointer.</param>
+        /// <param name="name">Name of the method.</param>
+        static void InitializeSlot(IntPtr type, IntPtr slot, string name)
+        {
+            Type typeOffset = typeof(TypeOffset);
+            FieldInfo fi = typeOffset.GetField(name);
+            var offset = (int)fi.GetValue(typeOffset);
+
+            Marshal.WriteIntPtr(type, offset, slot);
+        }
 
         /// <summary>
         /// Given a newly allocated Python type object and a managed Type that
diff --git a/src/testing/InheritanceTest.cs b/src/testing/InheritanceTest.cs
new file mode 100644
index 000000000..529703b3c
--- /dev/null
+++ b/src/testing/InheritanceTest.cs
@@ -0,0 +1,14 @@
+using System;
+
+namespace Python.Test
+{
+    public class BaseClass
+    {
+        public bool IsBase() => true;
+    }
+
+    public class DerivedClass : BaseClass
+    {
+        public new bool IsBase() => false;
+    }
+}
diff --git a/src/testing/Python.Test.15.csproj b/src/testing/Python.Test.15.csproj
new file mode 100644
index 000000000..da20ed2ef
--- /dev/null
+++ b/src/testing/Python.Test.15.csproj
@@ -0,0 +1,86 @@
+<Project>
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+  <PropertyGroup>
+    <TargetFrameworks>net40;netstandard2.0</TargetFrameworks>
+    <Platforms>x64;x86</Platforms>
+    <Configurations>DebugMono;DebugMonoPY3;ReleaseMono;ReleaseMonoPY3;DebugWin;DebugWinPY3;ReleaseWin;ReleaseWinPY3</Configurations>
+    <AssemblyName>Python.Test</AssemblyName>
+    <RootNamespace>Python.Test</RootNamespace>
+    <PackageId>Python.Test</PackageId>
+    <VersionPrefix>2.4.0</VersionPrefix>
+    <OutputPath>bin\</OutputPath>
+    <AppendTargetFrameworkToOutputPath Condition="'$(TargetFramework)'=='net40'">false</AppendTargetFrameworkToOutputPath>
+    <DocumentationFile Condition="'$(TargetFramework)'=='net40'">$(OutputPath)\$(AssemblyName).xml</DocumentationFile>
+    <DocumentationFile Condition="'$(TargetFramework)'!='net40'">$(OutputPath)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
+    <NoWarn>1591,0067</NoWarn>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <PythonBuildDir Condition=" '$(PythonBuildDir)' == '' ">$(SolutionDir)\bin\</PythonBuildDir>
+    <PythonBuildDir Condition="'$(TargetFramework)'!='net40'">$(PythonBuildDir)\$(TargetFramework)\</PythonBuildDir>
+    <LangVersion>6</LangVersion>
+    <SignAssembly>false</SignAssembly>
+    <AssemblyOriginatorKeyFile>..\pythonnet.snk</AssemblyOriginatorKeyFile>
+    <ErrorReport>prompt</ErrorReport>
+    <CustomDefineConstants Condition="'$(CustomDefineConstants)' == ''">$(PYTHONNET_DEFINE_CONSTANTS)</CustomDefineConstants>
+    <BaseDefineConstants>XPLAT</BaseDefineConstants>
+    <DefineConstants>$(DefineConstants);$(CustomDefineConstants);$(BaseDefineConstants);</DefineConstants>
+    <DefineConstants Condition="'$(BuildingInsideVisualStudio)' == 'true' AND '$(CustomDefineConstants)' != '' AND $(Configuration.Contains('Debug'))">$(DefineConstants);TRACE;DEBUG</DefineConstants>
+    <FrameworkPathOverride Condition="'$(TargetFramework)'=='net40' AND $(Configuration.Contains('Mono'))">$(NuGetPackageRoot)\microsoft.targetingpack.netframework.v4.5\1.0.1\lib\net45\</FrameworkPathOverride>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x86'">
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Platform)' == 'x64'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+  
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='net40'">
+    <Optimize>true</Optimize>
+    <DebugType>pdbonly</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Debug')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>false</Optimize>
+    <DebugType>full</DebugType>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release')) AND '$(TargetFramework)'=='netstandard2.0'">
+    <DebugSymbols>true</DebugSymbols>
+    <Optimize>true</Optimize>
+    <DebugType>portable</DebugType>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.Contains('Debug'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants);DEBUG;TRACE</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.Contains('Release'))">
+    <DefineConstants Condition="'$(CustomDefineConstants)' == ''">$(DefineConstants)</DefineConstants>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System" />
+  </ItemGroup>
+  
+  <ItemGroup>
+    <ProjectReference Include="..\runtime\Python.Runtime.15.csproj" />
+  </ItemGroup>
+  
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="Microsoft.CSharp" Version="4.4.0" />
+  </ItemGroup>
+
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+  <PropertyGroup>
+    <TargetAssembly>$(TargetPath)</TargetAssembly>
+    <TargetAssemblyPdb>$(TargetDir)$(TargetName).pdb</TargetAssemblyPdb>
+  </PropertyGroup>
+  <Target Name="AfterBuild">
+    <Copy Condition="'$(TargetFramework)'=='net40'" SourceFiles="$(TargetAssembly)" DestinationFolder="$(SolutionDir)\src\tests\fixtures" />
+    <Copy Condition="'$(TargetFramework)'!='net40'" SourceFiles="$(TargetAssembly)" DestinationFolder="$(SolutionDir)\src\tests\fixtures\$(TargetFramework)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
+  </Target>
+</Project>
diff --git a/src/testing/Python.Test.csproj b/src/testing/Python.Test.csproj
index ce8dca10d..27639ed5a 100644
--- a/src/testing/Python.Test.csproj
+++ b/src/testing/Python.Test.csproj
@@ -83,6 +83,7 @@
     <Compile Include="generictest.cs" />
     <Compile Include="globaltest.cs" />
     <Compile Include="indexertest.cs" />
+    <Compile Include="InheritanceTest.cs" />
     <Compile Include="interfacetest.cs" />
     <Compile Include="methodtest.cs" />
     <Compile Include="moduletest.cs" />
@@ -108,6 +109,6 @@
   </PropertyGroup>
   <Target Name="AfterBuild">
     <Copy SourceFiles="$(TargetAssembly)" DestinationFolder="$(SolutionDir)\src\tests\fixtures" />
-    <Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" />
+    <!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
   </Target>
-</Project>
+</Project>
\ No newline at end of file
diff --git a/src/testing/conversiontest.cs b/src/testing/conversiontest.cs
index 7179c7607..06ab7cb4e 100644
--- a/src/testing/conversiontest.cs
+++ b/src/testing/conversiontest.cs
@@ -32,8 +32,14 @@ public ConversionTest()
 
         public byte[] ByteArrayField;
         public sbyte[] SByteArrayField;
+
+        public T? Echo<T>(T? arg) where T: struct {
+            return arg;
+        }
+
     }
 
+    
 
     public interface ISpam
     {
@@ -54,4 +60,19 @@ public string GetValue()
             return value;
         }
     }
+    
+    public class UnicodeString
+    {
+        public string value = "안녕";
+
+        public string GetString()
+        {
+            return value;
+        }
+
+        public override string ToString()
+        {
+            return value;
+        }
+    }
 }
diff --git a/src/testing/exceptiontest.cs b/src/testing/exceptiontest.cs
index e4f683721..45acaa2cc 100644
--- a/src/testing/exceptiontest.cs
+++ b/src/testing/exceptiontest.cs
@@ -1,4 +1,6 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
 
 namespace Python.Test
 {
@@ -54,6 +56,13 @@ public static bool ThrowException()
             throw new OverflowException("error");
         }
 
+        public static IEnumerable<int> ThrowExceptionInIterator(Exception e)
+        {
+            yield return 1;
+            yield return 2;
+            throw e;
+        }
+
         public static void ThrowChainedExceptions()
         {
             try
diff --git a/src/testing/methodtest.cs b/src/testing/methodtest.cs
index 83dc907c0..cf653f9f9 100644
--- a/src/testing/methodtest.cs
+++ b/src/testing/methodtest.cs
@@ -666,3 +666,23 @@ public string PublicMethod(string echo)
         }
     }
 }
+
+namespace PlainOldNamespace
+{
+    public class PlainOldClass
+    {
+        public PlainOldClass() { }
+
+        public PlainOldClass(int param) { }
+
+        private readonly byte[] payload = new byte[(int)Math.Pow(2, 20)]; //1 MB
+
+        public void NonGenericMethod() { }
+
+        public void GenericMethod<T>() { }
+
+        public void OverloadedMethod() { }
+
+        public void OverloadedMethod(int param) { }
+    }
+}
diff --git a/src/tests/fixtures/netstandard2.0/.gitkeep b/src/tests/fixtures/netstandard2.0/.gitkeep
new file mode 100644
index 000000000..e69de29bb
diff --git a/src/tests/importtest.py b/src/tests/importtest.py
new file mode 100644
index 000000000..fe93764e9
--- /dev/null
+++ b/src/tests/importtest.py
@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+
+import sys
+try:
+    del sys.modules["System.IO"]
+except KeyError:
+    pass
+
+assert "FileStream" not in globals()
+import System.IO
+from System.IO import *
+
+assert "FileStream" in globals()
diff --git a/src/tests/test_class.py b/src/tests/test_class.py
index 68773508b..612ce442e 100644
--- a/src/tests/test_class.py
+++ b/src/tests/test_class.py
@@ -281,3 +281,14 @@ def PyCallback(self, self2):
     testobj.DoCallback()
     assert testobj.PyCallbackWasCalled
     assert testobj.SameReference
+
+
+def test_method_inheritance():
+    """Ensure that we call the overridden method instead of the one provided in
+       the base class."""
+
+    base = Test.BaseClass()
+    derived = Test.DerivedClass()
+
+    assert base.IsBase() == True
+    assert derived.IsBase() == False
diff --git a/src/tests/test_clrmethod.py b/src/tests/test_clrmethod.py
new file mode 100644
index 000000000..a6078bece
--- /dev/null
+++ b/src/tests/test_clrmethod.py
@@ -0,0 +1,73 @@
+# -*- coding: utf-8 -*-
+
+"""Test clrmethod and clrproperty support for calling methods and getting/setting python properties from CLR."""
+
+import Python.Test as Test
+import System
+import pytest
+import clr
+
+class ExampleClrClass(System.Object):
+    __namespace__ = "PyTest"
+    def __init__(self):
+        self._x = 3
+    @clr.clrmethod(int, [int])
+    def test(self, x):
+        return x*2
+    
+    def get_X(self):
+        return self._x
+    def set_X(self, value):
+        self._x = value
+    X = clr.clrproperty(int, get_X, set_X)
+
+    @clr.clrproperty(int)
+    def Y(self):
+        return self._x * 2
+
+def test_set_and_get_property_from_py():
+    """Test setting and getting clr-accessible properties from python."""
+    t = ExampleClrClass()
+    assert t.X == 3
+    assert t.Y == 3 * 2
+    t.X = 4
+    assert t.X == 4
+    assert t.Y == 4 * 2
+
+def test_set_and_get_property_from_clr():
+    """Test setting and getting clr-accessible properties from the clr."""
+    t = ExampleClrClass()
+    assert t.GetType().GetProperty("X").GetValue(t) == 3
+    assert t.GetType().GetProperty("Y").GetValue(t) == 3 * 2
+    t.GetType().GetProperty("X").SetValue(t, 4)
+    assert t.GetType().GetProperty("X").GetValue(t) == 4
+    assert t.GetType().GetProperty("Y").GetValue(t) == 4 * 2
+
+
+def test_set_and_get_property_from_clr_and_py():
+    """Test setting and getting clr-accessible properties alternatingly from the clr and from python."""
+    t = ExampleClrClass()
+    assert t.GetType().GetProperty("X").GetValue(t) == 3
+    assert t.GetType().GetProperty("Y").GetValue(t) == 3 * 2
+    assert t.X == 3
+    assert t.Y == 3 * 2
+    t.GetType().GetProperty("X").SetValue(t, 4)
+    assert t.GetType().GetProperty("X").GetValue(t) == 4
+    assert t.GetType().GetProperty("Y").GetValue(t) == 4 * 2
+    assert t.X == 4
+    assert t.Y == 4 * 2
+    t.X = 5
+    assert t.GetType().GetProperty("X").GetValue(t) == 5
+    assert t.GetType().GetProperty("Y").GetValue(t) == 5 * 2
+    assert t.X == 5
+    assert t.Y == 5 * 2
+
+def test_method_invocation_from_py():
+    """Test calling a clr-accessible method from python."""
+    t = ExampleClrClass()
+    assert t.test(41) == 41*2
+
+def test_method_invocation_from_clr():
+    """Test calling a clr-accessible method from the clr."""
+    t = ExampleClrClass()
+    assert t.GetType().GetMethod("test").Invoke(t, [37]) == 37*2
diff --git a/src/tests/test_conversion.py b/src/tests/test_conversion.py
index ac263ef5d..0ba10a80e 100644
--- a/src/tests/test_conversion.py
+++ b/src/tests/test_conversion.py
@@ -2,11 +2,12 @@
 
 """Test CLR <-> Python type conversions."""
 
+from __future__ import unicode_literals
 import System
 import pytest
-from Python.Test import ConversionTest
+from Python.Test import ConversionTest, UnicodeString
 
-from ._compat import indexbytes, long, unichr
+from ._compat import indexbytes, long, unichr, text_type, PY2, PY3
 
 
 def test_bool_conversion():
@@ -466,17 +467,6 @@ def test_double_conversion():
     with pytest.raises(TypeError):
         ConversionTest().DoubleField = None
 
-    with pytest.raises(OverflowError):
-        ConversionTest().DoubleField = 1.7976931348623159e308
-
-    with pytest.raises(OverflowError):
-        ConversionTest().DoubleField = -1.7976931348623159e308
-
-    with pytest.raises(OverflowError):
-        _ = System.Double(1.7976931348623159e308)
-
-    with pytest.raises(OverflowError):
-        _ = System.Double(-1.7976931348623159e308)
 
 
 def test_decimal_conversion():
@@ -546,6 +536,14 @@ def test_string_conversion():
 
     with pytest.raises(TypeError):
         ConversionTest().StringField = 1
+    
+    world = UnicodeString()
+    test_unicode_str = u"안녕"
+    assert test_unicode_str == text_type(world.value)
+    assert test_unicode_str == text_type(world.GetString())
+    # TODO: not sure what to do for Python 2 here (GH PR #670)
+    if PY3:
+        assert test_unicode_str == text_type(world)
 
 
 def test_interface_conversion():
@@ -641,6 +639,8 @@ def test_enum_conversion():
 
 def test_null_conversion():
     """Test null conversion."""
+    import System
+    
     ob = ConversionTest()
 
     ob.StringField = None
@@ -652,6 +652,10 @@ def test_null_conversion():
     ob.SpamField = None
     assert ob.SpamField is None
 
+    pi = 22/7
+    assert ob.Echo[System.Double](pi) == pi
+    assert ob.Echo[System.DateTime](None) is None
+
     # Primitive types and enums should not be set to null.
 
     with pytest.raises(TypeError):
diff --git a/src/tests/test_exceptions.py b/src/tests/test_exceptions.py
index f47209f6d..08b00d77d 100644
--- a/src/tests/test_exceptions.py
+++ b/src/tests/test_exceptions.py
@@ -289,7 +289,8 @@ def test_python_compat_of_managed_exceptions():
     assert e.args == (msg,)
     assert isinstance(e.args, tuple)
     if PY3:
-        assert repr(e) == "OverflowException('Simple message',)"
+        strexp = "OverflowException('Simple message"
+        assert repr(e)[:len(strexp)] == strexp
     elif PY2:
         assert repr(e) == "OverflowException(u'Simple message',)"
 
@@ -345,3 +346,44 @@ def test_chained_exceptions():
         assert exc.Message == msg
         assert exc.__cause__ == exc.InnerException
         exc = exc.__cause__
+
+def test_iteration_exception():
+    from Python.Test import ExceptionTest
+    from System import OverflowException
+
+    exception = OverflowException("error")
+
+    val = ExceptionTest.ThrowExceptionInIterator(exception).__iter__()
+    assert next(val) == 1
+    assert next(val) == 2
+    with pytest.raises(OverflowException) as cm:
+        next(val)
+
+    exc = cm.value
+
+    assert exc == exception
+
+    # after exception is thrown iterator is no longer valid
+    with pytest.raises(StopIteration):
+        next(val)
+
+
+def test_iteration_innerexception():
+    from Python.Test import ExceptionTest
+    from System import OverflowException
+
+    exception = System.Exception("message", OverflowException("error"))
+
+    val = ExceptionTest.ThrowExceptionInIterator(exception).__iter__()
+    assert next(val) == 1
+    assert next(val) == 2
+    with pytest.raises(OverflowException) as cm:
+        next(val)
+
+    exc = cm.value
+
+    assert exc == exception.InnerException
+
+    # after exception is thrown iterator is no longer valid
+    with pytest.raises(StopIteration):
+        next(val)
diff --git a/src/tests/test_import.py b/src/tests/test_import.py
index 42cafc4df..25877be15 100644
--- a/src/tests/test_import.py
+++ b/src/tests/test_import.py
@@ -3,7 +3,7 @@
 """Test the import statement."""
 
 import pytest
-
+import sys
 
 def test_relative_missing_import():
     """Test that a relative missing import doesn't crash.
@@ -11,3 +11,12 @@ def test_relative_missing_import():
     Relative import in the site-packages folder"""
     with pytest.raises(ImportError):
         from . import _missing_import
+
+
+def test_import_all_on_second_time():
+    """Test import all attributes after a normal import without '*'.
+    Due to import * only allowed at module level, the test body splited
+    to a module file."""
+    from . import importtest
+    del sys.modules[importtest.__name__]
+    
diff --git a/src/tests/test_method.py b/src/tests/test_method.py
index ad182678d..ad678611b 100644
--- a/src/tests/test_method.py
+++ b/src/tests/test_method.py
@@ -832,3 +832,137 @@ def test_case_sensitive():
 
     with pytest.raises(AttributeError):
         MethodTest.casesensitive()
+
+def test_getting_generic_method_binding_does_not_leak_ref_count():
+    """Test that managed object is freed after calling generic method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import sys
+
+    refCount = sys.getrefcount(PlainOldClass().GenericMethod[str])
+    assert refCount == 1
+
+def test_getting_generic_method_binding_does_not_leak_memory():
+    """Test that managed object is freed after calling generic method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import psutil, os, gc, clr
+
+    process = psutil.Process(os.getpid())
+    processBytesBeforeCall = process.memory_info().rss
+    print("\n\nMemory consumption (bytes) at start of test: " + str(processBytesBeforeCall))
+
+    iterations = 500
+    for i in range(iterations):
+        PlainOldClass().GenericMethod[str]
+
+    gc.collect()
+    clr.System.GC.Collect()
+
+    processBytesAfterCall = process.memory_info().rss
+    print("Memory consumption (bytes) at end of test: " + str(processBytesAfterCall))
+    processBytesDelta = processBytesAfterCall - processBytesBeforeCall
+    print("Memory delta: " + str(processBytesDelta))
+
+    bytesAllocatedPerIteration = pow(2, 20)  # 1MB
+    bytesLeakedPerIteration = processBytesDelta / iterations
+
+    # Allow 50% threshold - this shows the original issue is fixed, which leaks the full allocated bytes per iteration
+    failThresholdBytesLeakedPerIteration = bytesAllocatedPerIteration / 2
+
+    assert bytesLeakedPerIteration < failThresholdBytesLeakedPerIteration
+
+def test_getting_overloaded_method_binding_does_not_leak_ref_count():
+    """Test that managed object is freed after calling overloaded method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import sys
+
+    refCount = sys.getrefcount(PlainOldClass().OverloadedMethod.Overloads[int])
+    assert refCount == 1
+
+def test_getting_overloaded_method_binding_does_not_leak_memory():
+    """Test that managed object is freed after calling overloaded method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import psutil, os, gc, clr
+
+    process = psutil.Process(os.getpid())
+    processBytesBeforeCall = process.memory_info().rss
+    print("\n\nMemory consumption (bytes) at start of test: " + str(processBytesBeforeCall))
+
+    iterations = 500
+    for i in range(iterations):
+        PlainOldClass().OverloadedMethod.Overloads[int]
+
+    gc.collect()
+    clr.System.GC.Collect()
+
+    processBytesAfterCall = process.memory_info().rss
+    print("Memory consumption (bytes) at end of test: " + str(processBytesAfterCall))
+    processBytesDelta = processBytesAfterCall - processBytesBeforeCall
+    print("Memory delta: " + str(processBytesDelta))
+
+    bytesAllocatedPerIteration = pow(2, 20)  # 1MB
+    bytesLeakedPerIteration = processBytesDelta / iterations
+
+    # Allow 50% threshold - this shows the original issue is fixed, which leaks the full allocated bytes per iteration
+    failThresholdBytesLeakedPerIteration = bytesAllocatedPerIteration / 2
+
+    assert bytesLeakedPerIteration < failThresholdBytesLeakedPerIteration
+
+def test_getting_method_overloads_binding_does_not_leak_ref_count():
+    """Test that managed object is freed after calling overloaded method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import sys
+
+    refCount = sys.getrefcount(PlainOldClass().OverloadedMethod.Overloads)
+    assert refCount == 1
+
+def test_getting_method_overloads_binding_does_not_leak_memory():
+    """Test that managed object is freed after calling overloaded method. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import psutil, os, gc, clr
+
+    process = psutil.Process(os.getpid())
+    processBytesBeforeCall = process.memory_info().rss
+    print("\n\nMemory consumption (bytes) at start of test: " + str(processBytesBeforeCall))
+
+    iterations = 500
+    for i in range(iterations):
+        PlainOldClass().OverloadedMethod.Overloads
+
+    gc.collect()
+    clr.System.GC.Collect()
+
+    processBytesAfterCall = process.memory_info().rss
+    print("Memory consumption (bytes) at end of test: " + str(processBytesAfterCall))
+    processBytesDelta = processBytesAfterCall - processBytesBeforeCall
+    print("Memory delta: " + str(processBytesDelta))
+
+    bytesAllocatedPerIteration = pow(2, 20)  # 1MB
+    bytesLeakedPerIteration = processBytesDelta / iterations
+
+    # Allow 50% threshold - this shows the original issue is fixed, which leaks the full allocated bytes per iteration
+    failThresholdBytesLeakedPerIteration = bytesAllocatedPerIteration / 2
+
+    assert bytesLeakedPerIteration < failThresholdBytesLeakedPerIteration
+
+def test_getting_overloaded_constructor_binding_does_not_leak_ref_count():
+    """Test that managed object is freed after calling overloaded constructor, constructorbinding.cs mp_subscript. Issue #691"""
+
+    from PlainOldNamespace import PlainOldClass
+
+    import sys
+
+    # simple test
+    refCount = sys.getrefcount(PlainOldClass.Overloads[int])
+    assert refCount == 1
diff --git a/src/tests/test_module.py b/src/tests/test_module.py
index 2255ea411..62d79b9ab 100644
--- a/src/tests/test_module.py
+++ b/src/tests/test_module.py
@@ -352,6 +352,26 @@ def test_clr_add_reference():
     with pytest.raises(FileNotFoundException):
         AddReference("somethingtotallysilly")
 
+def test_clr_get_clr_type():
+    """Test clr.GetClrType()."""
+    from clr import GetClrType
+    import System
+    from System import IComparable
+    from System import ArgumentException
+    assert GetClrType(System.String).FullName == "System.String"
+    comparable = GetClrType(IComparable)
+    assert comparable.FullName == "System.IComparable"
+    assert comparable.IsInterface
+    assert GetClrType(int).FullName == "System.Int32"
+    assert GetClrType(str).FullName == "System.String"
+    assert GetClrType(float).FullName == "System.Double"
+    dblarr = System.Array[System.Double]
+    assert GetClrType(dblarr).FullName == "System.Double[]"
+
+    with pytest.raises(TypeError):
+        GetClrType(1)
+    with pytest.raises(TypeError):
+        GetClrType("thiswillfail")
 
 def test_assembly_load_thread_safety():
     from Python.Test import ModuleTest
@@ -367,3 +387,9 @@ def test_assembly_load_thread_safety():
         from System.Collections.Generic import Dictionary
         _ = Dictionary[Guid, DateTime]()
     ModuleTest.JoinThreads()
+
+def test_assembly_load_recursion_bug():
+    """Test fix for recursion bug documented in #627"""
+    from System.Configuration import ConfigurationManager
+    content = dir(ConfigurationManager)
+    assert len(content) > 5, content
diff --git a/src/tests/test_subclass.py b/src/tests/test_subclass.py
index 8e862a56d..ab440d429 100644
--- a/src/tests/test_subclass.py
+++ b/src/tests/test_subclass.py
@@ -15,12 +15,12 @@
 from ._compat import range
 
 
-def interface_test_class_fixture():
+def interface_test_class_fixture(subnamespace):
     """Delay creation of class until test starts."""
 
     class InterfaceTestClass(IInterfaceTest):
         """class that implements the test interface"""
-        __namespace__ = "Python.Test"
+        __namespace__ = "Python.Test." + subnamespace
 
         def foo(self):
             return "InterfaceTestClass"
@@ -31,12 +31,12 @@ def bar(self, x, i):
     return InterfaceTestClass
 
 
-def derived_class_fixture():
+def derived_class_fixture(subnamespace):
     """Delay creation of class until test starts."""
 
     class DerivedClass(SubClassTest):
         """class that derives from a class deriving from IInterfaceTest"""
-        __namespace__ = "Python.Test"
+        __namespace__ = "Python.Test." + subnamespace
 
         def foo(self):
             return "DerivedClass"
@@ -60,12 +60,12 @@ def return_list(self):
     return DerivedClass
 
 
-def derived_event_test_class_fixture():
+def derived_event_test_class_fixture(subnamespace):
     """Delay creation of class until test starts."""
 
     class DerivedEventTest(IInterfaceTest):
         """class that implements IInterfaceTest.TestEvent"""
-        __namespace__ = "Python.Test"
+        __namespace__ = "Python.Test." + subnamespace
 
         def __init__(self):
             self.event_handlers = []
@@ -85,7 +85,6 @@ def OnTestEvent(self, value):
     return DerivedEventTest
 
 
-@pytest.mark.skip(reason="FIXME: test randomly pass/fails")
 def test_base_class():
     """Test base class managed type"""
     ob = SubClassTest()
@@ -98,10 +97,9 @@ def test_base_class():
     assert list(SubClassTest.test_list(ob)) == ["a", "b", "c"]
 
 
-@pytest.mark.skip(reason="FIXME: test randomly pass/fails")
 def test_interface():
     """Test python classes can derive from C# interfaces"""
-    InterfaceTestClass = interface_test_class_fixture()
+    InterfaceTestClass = interface_test_class_fixture(test_interface.__name__)
     ob = InterfaceTestClass()
     assert ob.foo() == "InterfaceTestClass"
     assert FunctionsTest.test_foo(ob) == "InterfaceTestClass"
@@ -112,10 +110,9 @@ def test_interface():
     assert id(x) == id(ob)
 
 
-@pytest.mark.skip(reason="FIXME: test randomly pass/fails")
 def test_derived_class():
     """Test python class derived from managed type"""
-    DerivedClass = derived_class_fixture()
+    DerivedClass = derived_class_fixture(test_derived_class.__name__)
     ob = DerivedClass()
     assert ob.foo() == "DerivedClass"
     assert ob.base_foo() == "foo"
@@ -131,10 +128,42 @@ def test_derived_class():
     assert id(x) == id(ob)
 
 
-@pytest.mark.skip(reason="FIXME: test randomly pass/fails")
+def test_derived_traceback():
+    """Test python exception traceback in class derived from managed base"""
+    class DerivedClass(SubClassTest):
+        __namespace__ = "Python.Test.traceback"
+
+        def foo(self):
+            print (xyzname)
+            return None
+
+    import sys,traceback
+    ob = DerivedClass()
+
+    # direct call
+    try:
+        ob.foo()
+        assert False
+    except:
+        e = sys.exc_info()
+    assert "xyzname" in str(e[1])
+    location = traceback.extract_tb(e[2])[-1]
+    assert location[2] == "foo"
+
+    # call through managed code
+    try:
+        FunctionsTest.test_foo(ob)
+        assert False
+    except:
+        e = sys.exc_info()
+    assert "xyzname" in str(e[1])
+    location = traceback.extract_tb(e[2])[-1]
+    assert location[2] == "foo"
+
+
 def test_create_instance():
     """Test derived instances can be created from managed code"""
-    DerivedClass = derived_class_fixture()
+    DerivedClass = derived_class_fixture(test_create_instance.__name__)
     ob = FunctionsTest.create_instance(DerivedClass)
     assert ob.foo() == "DerivedClass"
     assert FunctionsTest.test_foo(ob) == "DerivedClass"
@@ -145,7 +174,7 @@ def test_create_instance():
     x = FunctionsTest.pass_through(ob)
     assert id(x) == id(ob)
 
-    InterfaceTestClass = interface_test_class_fixture()
+    InterfaceTestClass = interface_test_class_fixture(test_create_instance.__name__)
     ob2 = FunctionsTest.create_instance(InterfaceTestClass)
     assert ob2.foo() == "InterfaceTestClass"
     assert FunctionsTest.test_foo(ob2) == "InterfaceTestClass"
@@ -156,7 +185,6 @@ def test_create_instance():
     assert id(y) == id(ob2)
 
 
-@pytest.mark.skip(reason="FIXME: test randomly pass/fails")
 def test_events():
     class EventHandler(object):
         def handler(self, x, args):
@@ -169,12 +197,12 @@ def handler(self, x, args):
     assert FunctionsTest.test_event(x, 1) == 1
     assert event_handler.value == 1
 
-    InterfaceTestClass = interface_test_class_fixture()
+    InterfaceTestClass = interface_test_class_fixture(test_events.__name__)
     i = InterfaceTestClass()
     with pytest.raises(System.NotImplementedException):
         FunctionsTest.test_event(i, 2)
 
-    DerivedEventTest = derived_event_test_class_fixture()
+    DerivedEventTest = derived_event_test_class_fixture(test_events.__name__)
     d = DerivedEventTest()
     d.add_TestEvent(event_handler.handler)
     assert FunctionsTest.test_event(d, 3) == 3
@@ -193,3 +221,59 @@ def test_isinstance_check():
     for x in b:
         assert isinstance(x, System.Object)
         assert isinstance(x, System.String)
+
+def test_namespace_and_init():
+    calls = []
+    class TestX(System.Object):
+        __namespace__ = "test_clr_subclass_with_init_args"
+        def __init__(self, *args, **kwargs):
+            calls.append((args, kwargs))
+    t = TestX(1,2,3,foo="bar")
+    assert len(calls) == 1
+    assert calls[0][0] == (1,2,3)
+    assert calls[0][1] == {"foo":"bar"}
+
+def test_namespace_and_argless_init():
+    calls = []
+    class TestX(System.Object):
+        __namespace__ = "test_clr_subclass_without_init_args"
+        def __init__(self):
+            calls.append(True)
+    t = TestX()
+    assert len(calls) == 1
+    assert calls[0] == True
+
+
+def test_namespace_and_no_init():
+    class TestX(System.Object):
+        __namespace__ = "test_clr_subclass_without_init"
+        q = 1
+    t = TestX()
+    assert t.q == 1
+
+def test_construction_from_clr():
+    import clr
+    calls = []
+    class TestX(System.Object):
+        __namespace__ = "test_clr_subclass_init_from_clr"
+        @clr.clrmethod(None, [int, str])
+        def __init__(self, i, s):
+            calls.append((i, s))
+
+    # Construct a TestX from Python
+    t = TestX(1, "foo")
+    assert len(calls) == 1
+    assert calls[0][0] == 1
+    assert calls[0][1] == "foo"
+
+    # Reset calls and construct a TestX from CLR
+    calls = []
+    tp = t.GetType()
+    t2 = tp.GetConstructors()[0].Invoke(None)
+    assert len(calls) == 0
+
+    # The object has only been constructed, now it needs to be initialized as well
+    tp.GetMethod("__init__").Invoke(t2, [1, "foo"])
+    assert len(calls) == 1
+    assert calls[0][0] == 1
+    assert calls[0][1] == "foo"
diff --git a/tools/geninterop/fake_libc_include/crypt.h b/tools/geninterop/fake_libc_include/crypt.h
new file mode 100644
index 000000000..3b16d481f
--- /dev/null
+++ b/tools/geninterop/fake_libc_include/crypt.h
@@ -0,0 +1 @@
+#include "features.h"
\ No newline at end of file
diff --git a/tools/geninterop/geninterop.py b/tools/geninterop/geninterop.py
index bf5fdb96b..f8ef8e561 100644
--- a/tools/geninterop/geninterop.py
+++ b/tools/geninterop/geninterop.py
@@ -173,7 +173,8 @@ def preprocess_python_headers():
         "-D", "__attribute__(x)=",
         "-D", "__inline__=inline",
         "-D", "__asm__=;#pragma asm",
-        "-D", "__int64=long long"
+        "-D", "__int64=long long",
+        "-D", "_POSIX_THREADS"
     ]
 
     if hasattr(sys, "abiflags"):
@@ -185,7 +186,7 @@ def preprocess_python_headers():
             defines.extend(("-D", "PYTHON_WITH_WIDE_UNICODE"))
 
     python_h = os.path.join(include_py, "Python.h")
-    cmd = ["clang", "-I"] + include_dirs + defines + ["-E", python_h]
+    cmd = ["clang", "-pthread", "-I"] + include_dirs + defines + ["-E", python_h]
 
     # normalize as the parser doesn't like windows line endings.
     lines = []
diff --git a/tools/nuget/nuget.exe b/tools/nuget/nuget.exe
index e42e6d827..463f8e137 100644
Binary files a/tools/nuget/nuget.exe and b/tools/nuget/nuget.exe differ
diff --git a/tools/vswhere/vswhere.exe b/tools/vswhere/vswhere.exe
new file mode 100644
index 000000000..3eb2df009
Binary files /dev/null and b/tools/vswhere/vswhere.exe differ