Queue.Synchronized(Queue) Method

Definition

Namespace:

System.Collections

Assembly:

System.Collections.NonGeneric.dll

Source:

Queue.cs

Returns a new Queue that wraps the original queue, and is thread safe.

public:
 static System::Collections::Queue ^ Synchronized(System::Collections::Queue ^ queue);

public static System.Collections.Queue Synchronized (System.Collections.Queue queue);

static member Synchronized : System.Collections.Queue -> System.Collections.Queue

Public Shared Function Synchronized (queue As Queue) As Queue

Parameters

queue

Queue

The Queue to synchronize.

Returns

Queue

A Queue wrapper that is synchronized (thread safe).

Exceptions

ArgumentNullException

queue is null.

Examples

The following code example shows how to lock the collection using the SyncRoot during the entire enumeration. This method is an O(1) operation.

Queue^ myCollection = gcnew Queue();
bool lockTaken = false;
try
{
    Monitor::Enter(myCollection->SyncRoot, lockTaken);
    for each (Object^ item in myCollection);
    {
        // Insert your code here.
    }
}
finally
{
    if (lockTaken)
    {
        Monitor::Exit(myCollection->SyncRoot);
    }
}

Queue myCollection = new Queue();
lock (myCollection.SyncRoot)
{
    foreach (object item in myCollection)
    {
        // Insert your code here.
    }
}

Dim myCollection As New Queue()
SyncLock myCollection.SyncRoot
    For Each item In myCollection
        ' Insert your code here.
    Next item
End SyncLock

The following example shows how to synchronize a Queue, determine if a Queue is synchronized and use a synchronized Queue.

#using <system.dll>

using namespace System;
using namespace System::Collections;
int main()
{
   
   // Creates and initializes a new Queue.
   Queue^ myQ = gcnew Queue;
   myQ->Enqueue( "The" );
   myQ->Enqueue( "quick" );
   myQ->Enqueue( "brown" );
   myQ->Enqueue( "fox" );
   
   // Creates a synchronized wrapper around the Queue.
   Queue^ mySyncdQ = Queue::Synchronized( myQ );
   
   // Displays the sychronization status of both Queues.
   Console::WriteLine( "myQ is {0}.", myQ->IsSynchronized ? (String^)"synchronized" : "not synchronized" );
   Console::WriteLine( "mySyncdQ is {0}.", mySyncdQ->IsSynchronized ? (String^)"synchronized" : "not synchronized" );
}

/*
This code produces the following output.

myQ is not synchronized.
mySyncdQ is synchronized.
*/

using System;
using System.Collections;

public class SamplesQueue
{
    public static void Main()
    {
        // Creates and initializes a new Queue.
        Queue myQ = new Queue();
        myQ.Enqueue("The");
        myQ.Enqueue("quick");
        myQ.Enqueue("brown");
        myQ.Enqueue("fox");

        // Creates a synchronized wrapper around the Queue.
        Queue mySyncdQ = Queue.Synchronized(myQ);

        // Displays the sychronization status of both Queues.
        Console.WriteLine("myQ is {0}.", myQ.IsSynchronized ? "synchronized" : "not synchronized");
        Console.WriteLine("mySyncdQ is {0}.", mySyncdQ.IsSynchronized ? "synchronized" : "not synchronized");
    }
}
/*
This code produces the following output.

myQ is not synchronized.
mySyncdQ is synchronized.
*/

Imports System.Collections

Public Class SamplesQueue    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new Queue.
        Dim myQ As New Queue()
        myQ.Enqueue("The")
        myQ.Enqueue("quick")
        myQ.Enqueue("brown")
        myQ.Enqueue("fox")
        
        ' Creates a synchronized wrapper around the Queue.
        Dim mySyncdQ As Queue = Queue.Synchronized(myQ)
        
        ' Displays the sychronization status of both Queues.
        Dim msg As String
        If myQ.IsSynchronized Then
            msg = "synchronized"
        Else
            msg = "not synchronized"
        End If
        Console.WriteLine("myQ is {0}.", msg)
        If mySyncdQ.IsSynchronized Then
            msg = "synchronized"
        Else
            msg = "not synchronized"
        End If
        Console.WriteLine("mySyncdQ is {0}.", msg)
    End Sub
End Class

' This code produces the following output.
' 
' myQ is not synchronized.
' mySyncdQ is synchronized.

Remarks

The wrapper returned by this method locks the queue before an operation is performed so that it is performed in a thread-safe manner.

To guarantee the thread safety of the Queue, all operations must be done through this wrapper only.

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. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

See also

• IsSynchronized
• SyncRoot