Async call to WCF with C#?

In C#, how do I make an async call to a WCF Web Service? I have a Service Reference set up to generate async. I also modified my calls to use { WebServiceObject.Begin* () } but there are two parameters at the end, 'AsyncCallback' and 'object asyncState'. What are these and how do I use them?

Thanks,

From stackoverflow

• See MSDN here; http://msdn.microsoft.com/en-us/library/system.asynccallback.aspx

  here; http://msdn.microsoft.com/en-us/library/ms228969.aspx

  here; http://msdn.microsoft.com/en-us/library/ms228975.aspx

  and here; http://msdn.microsoft.com/en-us/library/86wf6409.aspx

  Basicly in Begin* you set an callback, that callback is called when the operation has completed. There you call End* to retrieve the appropriate data.

  Phillip : Got it. Thanks.

• Callback is called when operation is completed, so you can call End* and grab return value or exception if any. asyncState is just a value for matching in callback if you use same callback method in several places. Here is a description of Async design pattern - http://msdn.microsoft.com/en-us/library/aa719595(VS.71).aspx

  If you are creating GUI application, consider using another version - *Async method which is generated for each operation as well. It provides thread synchronization.

• You might also want to look at Async without the Pain