Jon

I believe I understood your question a little differently than Cesar
did. As I understand it, you want the client to call the server
synchronously and have the web service respond immediately. Then you
want the web service to kick a new set of code after the response to
the client has been made. You don't want your client to have to worry
about any asynchronous actions.

In that case, you don't want to use an asynchronous web service call.
Just call your web service as you normally do, but have you web service
spawn a new thread that will launch the asynchronous code. I've
included an example below.

   <WebMethod()> _
   Public Function HelloWorld() As String
       'create your new thread
       Dim thread As New System.Threading.Thread(AddressOf
RunAsync_Proc)

       'start the async thread
       thread.Start()

       'respond to your client while the other thread is still running
       Return "Hello World"
   End Function

   Public Sub RunAsync_Proc()

       'Put code here to do your asynchronous processing

   End Sub

If you're interested, there is another option. You could potentially
use the SOAPDocumentMethodAttribute.OneWay property that is already
built into the .NET framework . It allows you to create web services
that automatically respond to the client before they begin their own
processing.

You can read more about this property at

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlr
fsystemwebservicesprotocolssoapdocumentmethodattributeclassonewaytopic.asp

Hope that helps.

Peter Kelcey