Windows apps
Collapse the table of content
Expand the table of content
Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

BackgroundWorker::CancelAsync Method ()

 

Requests cancellation of a pending background operation.

Namespace:   System.ComponentModel
Assembly:  System (in System.dll)

public:
void CancelAsync()

CancelAsync submits a request to terminate the pending background operation and sets the CancellationPending property to true.

When you call CancelAsync, your worker method has an opportunity to stop its execution and exit. The worker code should periodically check the CancellationPending property to see if it has been set to true.

System_CAPS_cautionCaution

Be aware that your code in the DoWork event handler may finish its work as a cancellation request is being made, and your polling loop may miss CancellationPending being set to true. In this case, the Cancelled flag of System.ComponentModel::RunWorkerCompletedEventArgs in your RunWorkerCompleted event handler will not be set to true, even though a cancellation request was made. This situation is called a race condition and is a common concern in multithreaded programming. For more information about multithreading design issues, see Managed Threading Best Practices.

The following code example demonstrates the use of the CancelAsync method to cancel an asynchronous ("background") operation. This code example is part of a larger example provided for the BackgroundWorker class.

void cancelAsyncButton_Click( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
{  
   // Cancel the asynchronous operation.
   this->backgroundWorker1->CancelAsync();

   // Disable the Cancel button.
   cancelAsyncButton->Enabled = false;
}

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Return to top
Show:
© 2017 Microsoft