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 Next Article C# | Check if ListDictionary is synchronized (thread safe) K Kirti_Mangal Follow Improve Article Tags : C# CSharp-Collections-Namespace CSharp-Collections-ArrayList Similar Reads C# | Check if the BitArray is synchronized (thread safe) 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.IsSynchronized property is used to get a value indi 2 min read C# | Check if an array is synchronized (thread safe) or not Array.IsSynchronized Property is used to get a value which indicates whether access to the Array is synchronized (thread-safe) or not. Syntax: public bool IsSynchronized { get; } Property Value: This property always returns false for all arrays. Below programs illustrate the use of above-discussed p 2 min read C# | Check if Hashtable is synchronized (thread safe) Hashtable.IsSynchronized Property is used to get a value indicating whether access to the Hashtable is synchronized(thread-safe). Syntax: public virtual bool IsSynchronized { get; } Return Value: This property return true if access to the Hashtable is synchronized (thread-safe), otherwise it returns 2 min read C# | Check if ListDictionary is synchronized (thread safe) ListDictionary.IsSynchronized property is used to get a value indicating whether the ListDictionary is synchronized (thread safe) or not. Syntax: public bool IsSynchronized { get; } Return Value: This property always returns false. Below are the programs to illustrate the use of ListDictionary.IsSyn 1 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# | Creating a synchronized (thread-safe) wrapper for the ArrayList Synchronized(ArrayList) method is used to get an ArrayList wrapper that is synchronized (thread safe). Syntax: public static System.Collections.ArrayList Synchronized (System.Collections.ArrayList list); Here, the list is the ArrayList which is to be synchronized. Return Value: It returns an ArrayLi 2 min read Like