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C# in a Nutshell by Peter Drayton, Ted Neward, Ben Albahari

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Name

AsyncCallback

Synopsis

This delegate type is used as part of asynchronous operations on delegates in general. As described in Chapter 16, delegates can be executed in an asynchronous fashion, using a random thread out of the system-managed thread pool. Frequently, however, programmers desire notification of the asynchronously executing delegate’s completion, and the AsyncCallback is used to achieve that.

Using an AsyncCallback is fairly straightforward. At the asynchronous delegate’s invocation, pass in an instance of this delegate (referring to a void-returning IAsyncResult-accepting method) as part of the BeginInvoke() call. When the asynchronously executing delegate has finished execution, the method on the other end of the AsyncCallback is invoked, with an IAsyncResult object as the sole parameter. (This IAsyncResult object contains the output parameters from the delegate’s call: the return value, along with any out or ref parameters declared as part of the method’s signature.)

public delegate void AsyncCallback(IAsyncResult ar);  

Passed To

Multiple types

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