C# | Check if ArrayList is Synchronized (thread safe) Last Updated : 11 Jul, 2025 Comments Improve Suggest changes Like Article Like Report ArrayList.IsSynchronized Property is used to get a value which indicate whether access to the ArrayList is synchronized (thread safe). Syntax: public virtual bool IsSynchronized { get; } Return Value: This property returns the true if access to the ArrayList is synchronized (thread safe) otherwise it returns false. The default is false. Below programs illustrate the use of above-discussed property: Example 1: CSharp // C# code to check if ArrayList // Is Synchronized or not using System; using System.Collections; class GFG { // Driver code public static void Main() { // Creating an ArrayList ArrayList myList = new ArrayList(); // Adding elements to ArrayList myList.Add("A"); myList.Add("B"); myList.Add("C"); myList.Add("D"); myList.Add("E"); myList.Add("F"); // Creates a synchronized // wrapper around the ArrayList ArrayList smyList = ArrayList.Synchronized(myList); // Displays the synchronization // status of both ArrayList Console.WriteLine("myList is {0}.", myList.IsSynchronized ? "Synchronized" : "Not Synchronized"); Console.WriteLine("smyList is {0}.", smyList.IsSynchronized ? "Synchronized" : "Not Synchronized"); } } Output: myList is Not Synchronized. smyList is Synchronized. Example 2: CSharp // C# code to check if ArrayList // Is Synchronized or not using System; using System.Collections; class GFG { // Driver code public static void Main() { // Creating an ArrayList ArrayList myList = new ArrayList(); // Adding elements to ArrayList myList.Add(1); myList.Add(2); myList.Add(3); myList.Add(4); myList.Add(5); myList.Add(5); // the default is false for // IsSynchronized property Console.WriteLine(myList.IsSynchronized); } } Output: False Note: Retrieving the value of this property is an O(1) operation. To guarantee the thread safety of the ArrayList, all operations must be done through the wrapper returned by the Synchronized method. Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. Reference: https://learn.microsoft.com/en-us/dotnet/api/system.collections.arraylist.issynchronized?view=netframework-4.7.2 Comment More infoAdvertise with us K Kirti_Mangal Follow Improve Article Tags : C# CSharp-Collections-Namespace CSharp-Collections-ArrayList Explore IntroductionC# Tutorial 4 min read Introduction to .NET Framework 6 min read C# .NET Framework (Basic Architecture and Component Stack) 6 min read C# Hello World 4 min read Common Language Runtime (CLR) in C# 4 min read FundamentalsC# Identifiers 2 min read C# Data Types 7 min read C# Variables 4 min read C# Literals 5 min read C# Operators 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 C# Loops 4 min read C# Jump Statements (Break, Continue, Goto, Return and Throw) 4 min read OOP ConceptsC# Class and Objects 5 min read C# Constructors 5 min read C# Inheritance 6 min read C# Encapsulation 4 min read C# Abstraction 4 min read MethodsC# Methods 4 min read C# Method Overloading 4 min read C# | Method Parameters 7 min read C# Method Overriding 9 min read Anonymous Method in C# 3 min read ArraysC# Arrays 8 min read C# Jagged Arrays 4 min read C# Array Class 7 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 StringC# Strings 7 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 4 min read C# Multidimensional Indexers 5 min read C# - Overloading of Indexers 3 min read Like