C# | Check if an array is read-only or not Last Updated : 01 Feb, 2019 Summarize Comments Improve Suggest changes Share 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 K Kirti_Mangal Follow Improve Article Tags : C# CSharp-Arrays Similar Reads C# Tutorial C# (pronounced "C-sharp") is a modern, versatile, object-oriented programming language developed by Microsoft in 2000 that runs on the .NET Framework. 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