ConcurrentQueue(Of T).TryDequeue Method (T)

.NET Framework (current version)

Tries to remove and return the object at the beginning of the concurrent queue.

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

Public Function TryDequeue (
	<OutAttribute> ByRef result As T
) As Boolean


Type: T

When this method returns, if the operation was successful, result contains the object removed. If no object was available to be removed, the value is unspecified.

Return Value

Type: System.Boolean

true if an element was removed and returned from the beginning of the ConcurrentQueue(Of T) successfully; otherwise, false.

ConcurrentQueue(Of T) handles all synchronization internally. If two threads call TryDequeue at precisely the same moment, neither operation is blocked. When a conflict is detected between two threads, one thread has to try again to retrieve the next element, and the synchronization is handled internally.

TryDequeue tries to remove an element from the queue. If the method is successful, the item is removed and the method returns true; otherwise, it returns false. That happens atomically with respect to other operations on the queue. If the queue was populated with code such as q.Enqueue("a"); q.Enqueue("b"); q.Enqueue("c"); and two threads concurrently try to dequeue an element, one thread will dequeue a and the other thread will dequeue b. Both calls to TryDequeue will return true, because they were both able to dequeue an element. If each thread goes back to dequeue an additional element, one of the threads will dequeue c and return true, whereas the other thread will find the queue empty and will return false.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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