AsyncCallback Delegate

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

References a method to be called when a corresponding asynchronous operation is completed.

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


Public Delegate Sub AsyncCallback ( _
    ar As IAsyncResult _
public delegate void AsyncCallback(
    IAsyncResult ar



Use an AsyncCallback delegate to process the results of an asynchronous operation in a separate thread. The AsyncCallback delegate represents a callback method that is called when the asynchronous operation is completed. The callback method takes an IAsyncResult parameter, which is subsequently used to obtain the results of the asynchronous operation.

Version Notes

Windows Phone

Asynchronous delegate calls, specifically the BeginInvoke and EndInvoke methods, are not supported in Windows Phone. If you attempt to invoke delegates asynchronously, the application throws TargetInvocationException instead of NotSupportedException.

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0


Windows Phone

See Also


System Namespace