Queue.Synchronized() Method in C#

Last Updated : 11 Jul, 2025
This method is used to return a new Queue that wraps the original queue and is thread-safe. The wrapper returned by this method locks the queue before an operation is performed so that it is performed in a thread-safe manner. Syntax:
public static System.Collections.Queue Synchronized (System.Collections.Queue queue);
Return Value: A Queue wrapper that is synchronized (thread safe). Exception: This method will give ArgumentNullException if the queue is null. Below programs illustrate the use of above-discussed method: Example 1: csharp 
// C# code to illustrate the
// Queue.Synchronized() Method
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Queue
        Queue myQueue = new Queue();

        // Inserting the elements into the Queue
        myQueue.Enqueue("C");
        myQueue.Enqueue("C++");
        myQueue.Enqueue("Java");
        myQueue.Enqueue("C#");
        myQueue.Enqueue("HTML");
        myQueue.Enqueue("CSS");

        // Creates a synchronized
        // wrapper around the Queue
        Queue sq = Queue.Synchronized(myQueue);

        // Displays the synchronization
        // status of both ArrayList
        Console.WriteLine("myQueue is {0}.", myQueue.IsSynchronized ?
                                "Synchronized" : "Not Synchronized");

        Console.WriteLine("sq is {0}.", sq.IsSynchronized ? 
                      "Synchronized" : "Not Synchronized");
    }
}
Output: 
myQueue is Not Synchronized.
sq is Synchronized.
Example 2: csharp 
// C# code to illustrate the
// Queue.Synchronized() Method
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Queue
        Queue myQueue = new Queue();

        // Inserting the elements into the Queue
        myQueue.Enqueue("Geeks");
        myQueue.Enqueue("for");
        myQueue.Enqueue("Geeks");
        myQueue.Enqueue("Noida");
        myQueue.Enqueue("Sector");
        myQueue.Enqueue("142");

        // it will give error as
        // the parameter is null
        Queue smyList = Queue.Synchronized(null);
    }
}
Runtime Error:
Unhandled Exception: System.ArgumentNullException: Value cannot be null. Parameter name: queue
Reference:
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