AsyncResult.AsyncWaitHandle Property

abstract AsyncWaitHandle : WaitHandle with get 
override AsyncWaitHandle : WaitHandle with get

Implements

The WaitHandle returned by this method is automatically signaled when the asynchronous operation has completed.

The wait handle is not closed automatically when you call EndInvoke on the delegate that was used to make the asynchronous method call. If you release all references to the wait handle, system resources are freed when garbage collection reclaims the wait handle. To free the system resources as soon as you are finished using the wait handle, call the WaitHandle.Close method. Garbage collection works more efficiently when disposable objects are explicitly closed or disposed.

Caution

The WaitHandle contained in the AsyncWaitHandle property can be used to block the current thread until the asynchronous call is complete. However the WaitHandle will ignore the AsyncCallback, if one was specified during the BeginInvoke call. Therefore, a situation can occur where the application shuts down before the AsyncCallback has finished executing, even if a WaitHandle is used to block until the asynchronous call completion. For an example of such a situation, see the example for the AsyncResult class, and remove the Thread.Sleep statement.

The following example demonstrates how to use the AsyncWaitHandle property to get a WaitHandle, and how to wait for an asynchronous call on a delegate. The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.

The example consists of two classes, the class that contains the method which is called asynchronously, and the class that contains the Main method that makes the call.

For more information and more examples of calling methods asynchronously by using delegates, see Calling Synchronous Methods Asynchronously.

.NET Framework

.NET Framework Client Profile

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

Reference

Other Resources