C# | Check if an array is read-only or not Last Updated : 01 Feb, 2019 Comments Improve Suggest changes Like Article Like Report Array.IsReadOnly Property is used to get a value that indicates whether the Array is read-only or not. Syntax: public bool IsReadOnly { get; } Property Value: This property always returns false for all arrays. Below programs illustrate the use of above-discussed property: Example 1: CSharp // C# program to illustrate // IsReadOnly Property of // Array class using System; namespace geeksforgeeks { class GFG { // Main Method public static void Main() { // declares an 1D Array of string string[] topic; // assigning null to array topic = new string[] { null }; // Here we check whether is // array of fixed size or not Console.WriteLine("Result: " + topic.IsReadOnly); } } } Output: Result: False Example 2: CSharp // C# program to illustrate // IsReadOnly Property of // Array class using System; namespace geeksforgeeks { class GFG { // Main Method public static void Main() { // Two-dimensional array int[, ] arr = new int[, ] {{1, 2}, {3, 4}, {5, 6}, {7, 8}}; // Here we check whether is // array of fixed size or not Console.WriteLine("Result: " + arr.IsReadOnly); } } } Output: Result: False Note: Array implements the IsReadOnly property because it is needed by the System.Collections.IList interface. An array which is read-only does not allow the addition, removal, or modification of elements after the creation of an array. If a user requires a read-only collection, then he or she must use a System.Collections class which implements the System.Collections.IList interface. If a user cast or convert an array to an IList interface object, the IList.IsReadOnly property returns false. However, if the user cast or convert an array to an IList<T> interface, the IsReadOnly property returns true. Retrieving the value of this property is an O(1) operation. Reference: https://docs.microsoft.com/en-us/dotnet/api/system.array.isreadonly?view=netframework-4.7.2 Comment More infoAdvertise with us Next Article C# | Check if an array is read-only or not K Kirti_Mangal Follow Improve Article Tags : C# CSharp-Arrays Similar Reads C# | Check if the BitArray is read-only The BitArray class manages a compact array of bit values, which are represented as Booleans, where true indicates that the bit is on i.e, 1 and false indicates the bit is off i.e, 0. This class is contained in System.Collections namespace. BitArray.IsReadOnly property is used to get a value indicati 2 min read C# | Check if the ArrayList is read-only ArrayList represents an ordered collection of an object that can be indexed individually. It is basically an alternative to an array. It also allows dynamic memory allocation, adding, searching and sorting items in the list. ArrayList.IsReadOnly property is used to check whether the ArrayList is rea 2 min read C# | Check if an Array has fixed size or not Array.IsFixedSize Property is used to get a get a value indicating whether the Array has a fixed size. This property implements the IList.IsFixedSize Property . Syntax: public bool IsFixedSize { get; } Property Value: This property is always return true for all arrays. Below programs illustrate the 2 min read C# | Check if a SortedList is read-only SortedList class is a collection of (key, value) pairs which are sorted according to keys. Those pairs can be accessible by key and as well as by index(zero-based indexing). This comes under System.Collections namespace. SortedList.IsReadOnly property is used to get a value which indicates that a So 2 min read C# | Check if ListDictionary is read-only ListDictionary.IsReadOnly property is used to get a value indicating whether the ListDictionary is read-only or not. Syntax: public bool IsReadOnly { get; } Return Value : This property always returns false. Example: CSHARP // C# code to check if ListDictionary is read-only using System; using Syste 1 min read Like