References the callback method to be called when the asynchronous operation is completed.
C# Syntax:
[Serializable] public delegate void AsyncCallback(IAsyncResult ar);
Parameters:
The declaration of your event handler must have the same parameters as the
AsyncCallback delegate declaration.
ar
The result of the asynchronous operation.
Remarks
AsyncCallback provides a way for client applications to complete an asynchronous operation. This callback delegate is supplied to the client when the asynchronous operation is initiated. The event handler referenced by AsyncCallback contains program logic to finish processing the asynchronous task for the client.