C# | Getting the index of the specified key in a SortedList object Last Updated : 01 Feb, 2019 Comments Improve Suggest changes Like Article Like Report SortedList.IndexOfKey(Object) Method is used to get the zero-based index of the specified key in a SortedList object. Syntax: public virtual int IndexOfKey (object key); Here, key is the Key which is to be located in the SortedList object. Return Value: This method returns the zero-based index of type System.Int32 of the key parameter if the key is found in the SortedList object otherwise it returns -1. Exceptions: ArgumentNullException: If the key is null. InvalidOperationException: If the comparer throws an exception. Below programs illustrate the use of above-discussed method: Example 1: CSharp // C# code to get the zero-based index // of the specified key in a SortedList // object using System; using System.Collections; class Geeks { // Main Method public static void Main(String[] args) { // Creating a SortedList of integers SortedList mylist = new SortedList(); // Adding elements to SortedList mylist.Add("First", "Ram"); mylist.Add("Second", "Shyam"); mylist.Add("Third", "Mohit"); mylist.Add("Fourth", "Rohit"); mylist.Add("Fifth", "Manish"); // printing the keys and values of mylist Console.WriteLine("Index \t\t Keys \t\tValues"); for (int i = 0; i < mylist.Count; i++) { Console.WriteLine("[{0}]\t\t{1}\t\t{2}", i, mylist.GetKey(i), mylist.GetByIndex(i)); } Console.Write("\nThe index of key 'Third' is: "); // getting the index of key "Third" Console.Write(mylist.IndexOfKey("Third")); // getting the index of key which is // not present in mylist so it will // return -1 Console.Write("\nThe index of key 'Sixth' is: "); Console.Write(mylist.IndexOfKey("Sixth")); } } Output: Index Keys Values [0] Fifth Manish [1] First Ram [2] Fourth Rohit [3] Second Shyam [4] Third Mohit The index of key 'Third' is: 4 The index of key 'Sixth' is: -1 Example 2: To demonstrate the case where ArgumentNullException can occur CSharp // C# code to get the zero-based index // of the specified key in a SortedList // object using System; using System.Collections; class Geeks { // Main Method public static void Main(String[] args) { // Creating a SortedList of integers SortedList mylist = new SortedList(); // Adding elements to SortedList mylist.Add("1", "C++"); mylist.Add("2", "Java"); mylist.Add("3", "DSA"); mylist.Add("4", "Python"); mylist.Add("5", "C#"); // printing the keys and values of mylist Console.WriteLine("Index \t\t Keys \t\tValues"); for (int i = 0; i < mylist.Count; i++) { Console.WriteLine("[{0}]\t\t{1}\t\t{2}", i, mylist.GetKey(i), mylist.GetByIndex(i)); } Console.Write("\nThe index of key 'null' is: "); // getting the index of key "null" // it will give ArgumentNullException Console.Write(mylist.IndexOfKey(null)); } } Runtime Error: Unhandled Exception: System.ArgumentNullException: Key cannot be null. Parameter name: key Note: The index sequence is based on the sort sequence. When an element is added, it is inserted into SortedList in the correct sort order, and the indexing adjusts accordingly. When an element is removed, the indexing also adjusts accordingly. So, the index of a specific key/value pair may change. This method uses a binary search algorithm so, this method is an O(log n) operation, where n is the Count. Reference: https://docs.microsoft.com/en-us/dotnet/api/system.collections.sortedlist.indexofkey?view=netframework-4.7.2 Comment More infoAdvertise with us Next Article C# | Getting the index of the specified key in a SortedList object K Kirti_Mangal Follow Improve Article Tags : C# CSharp-method CSharp-Collections-Namespace CSharp-Collections-SortedList Similar Reads C# | Getting the key at the specified index of a SortedList object SortedList.GetKey(Int32) Method is used to get the key at the specified index of a SortedList object. Syntax: public virtual object GetKey (int index); Here, index is the zero-based index of the key to get. Return Value: This method returns the key at the specified index of the SortedList object. Ex 2 min read C# | Getting index of the specified value in a SortedList object SortedList.IndexOfValue(Object) Method is used to get the zero-based index of the first occurrence of the specified value in a SortedList object. Syntax: public virtual int IndexOfValue (object value); Here, value is the Value which is to be located in the SortedList object. The value can be null. R 3 min read C# | Getting the value at the specified index of a SortedList object SortedList.GetByIndex(Int32) Method is used to get the value at the specified index of a SortedList object. Syntax: public virtual object GetByIndex (int index); Here index is the zero-based index of the value to get. Return Value: It returns the value at the specified index of the SortedList object 2 min read C# | Getting the keys in a SortedList object SortedList.Keys Property is used to get the keys in a SortedList object. Syntax: public virtual System.Collections.ICollection Keys { get; } Property Value: An ICollection object containing the keys in the SortedList object. Below programs illustrate the use of above-discussed property: Example 1: C 2 min read C# | Check whether a SortedList object contains a specific key SortedList.Contains(Object) Method is used to check whether a SortedList object contains a specific key. Syntax: public virtual bool Contains (object key); Here, key is the Key which is to be located in the SortedList object. Return Value: This method returns the true if the SortedList object contai 2 min read Like