Export (0) Print
Expand All

WorkflowQueue.Dequeue Method

Removes and returns the object at the beginning of the WorkflowQueue.

Namespace:  System.Workflow.Runtime
Assembly:  System.Workflow.Runtime (in System.Workflow.Runtime.dll)

public Object Dequeue()

Return Value

Type: System.Object
The object that is removed from the beginning of the WorkflowQueue.

ExceptionCondition
InvalidOperationException

The WorkflowQueue is empty.

You can check Count to determine whether the WorkflowQueue is empty before you call Dequeue, or you can catch the InvalidOperationException.

The following code example demonstrates how you can create a WorkflowQueue by calling the WorkflowQueuingService.GetWorkflowQueue method. It also uses the Count property to determine whether any messages exist in the current queue. Finally, the code uses the Dequeue method to remove and return the first object in the queue.

This code example is part of the File Watcher Activity SDK Sample from the FileSystemEvent.cs file. For more information, see File System Watcher Activity.

private bool ProcessQueueItem(ActivityExecutionContext context)
{
    WorkflowQueuingService qService = context.GetService<WorkflowQueuingService>();
    if (!qService.Exists(this.QueueName))
    {
        return false;
    }

    WorkflowQueue queue = qService.GetWorkflowQueue(this.QueueName);

    // If the queue has messages, then process the first one 
    if (queue.Count == 0)
    {
        return false;
    }

    FileWatcherEventArgs e = (FileWatcherEventArgs)queue.Dequeue();

    // Raise the FileSystemEvent 
    base.RaiseGenericEvent<FileWatcherEventArgs>(FileSystemEvent.FileWatcherEventHandlerEvent, this, e);

    DoUnsubscribe(context, this);
    DeleteQueue(context);
    return true;
}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0

Community Additions

ADD
Show:
© 2015 Microsoft