Queue.Synchronized Method (Queue)


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

Namespace:   System.Collections
Assembly:  mscorlib (in mscorlib.dll)

<HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization := True)>
Public Shared Function Synchronized (
	queue As Queue
) As Queue


Type: System.Collections.Queue

The Queue to synchronize.

Return Value

Type: System.Collections.Queue

A Queue wrapper that is synchronized (thread safe).

Exception Condition

queue is null.

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.

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

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.

Imports System
Imports System.Collections

Public Class SamplesQueue    

    Public Shared Sub Main()

        ' Creates and initializes a new Queue.
        Dim myQ As New Queue()

        ' 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"
            msg = "not synchronized"
        End If
        Console.WriteLine("myQ is {0}.", msg)
        If mySyncdQ.IsSynchronized Then
            msg = "synchronized"
            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. 

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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