C# | Check if an array is read-only or not Last Updated : 11 Jul, 2025 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://learn.microsoft.com/en-us/dotnet/api/system.array.isreadonly?view=netframework-4.7.2 Comment K Kirti_Mangal Follow 0 Improve K Kirti_Mangal Follow 0 Improve Article Tags : C# CSharp-Arrays Explore IntroductionC# Tutorial 2 min read Introduction to .NET Framework 6 min read C# .NET Framework (Basic Architecture and Component Stack) 6 min read C# Hello World 2 min read Common Language Runtime (CLR) in C# 4 min read FundamentalsC# Identifiers 2 min read Data Types in C# 6 min read C# Variables 4 min read C# Literals 5 min read Operators in C# 7 min read C# Keywords 5 min read Control StatementsC# Decision Making (if, if-else, if-else-if ladder, nested if, switch, nested switch) 5 min read C# Switch Statement 4 min read Loops in C# 4 min read C# Jump Statements (Break, Continue, Goto, Return and Throw) 4 min read OOP ConceptsClass and Objects in C# 4 min read Constructors in C# 5 min read C# Inheritance 3 min read Encapsulation in C# 2 min read C# Abstraction 4 min read MethodsMethods in C# 4 min read Method Overloading in C# 4 min read Method Parameters in C# 4 min read Method Overriding in C# 7 min read Anonymous Method in C# 2 min read ArraysArrays in C# 6 min read Jagged Arrays in C# 4 min read Array Class in C# 5 min read How to Sort an Array in C# | Array.Sort() Method Set - 1 8 min read How to find the rank of an array in C# 2 min read ArrayListArrayList in C# 6 min read C# ArrayList Class 7 min read C# | Array vs ArrayList 2 min read StringStrings in C# 6 min read C# Verbatim String Literal - @ 5 min read C# String Class 9 min read C# StringBuilder 4 min read C# String vs StringBuilder 3 min read TupleC# Tuple 7 min read C# Tuple Class 3 min read C# ValueTuple 7 min read C# ValueTuple Struct 4 min read IndexersC# Indexers 5 min read C# Multidimensional Indexers 5 min read C# - Overloading of Indexers 3 min read Like