The asynchronous design pattern in the common language runtime involves calling a Begin method to start the asynchronous method invocation and an End method to complete the invocation. The Begin method takes two additional parameters besides the parameters defined by the synchronous version of the method: one to store a delegate and one to store any state information that needs to be passed on to the delegate. This property represents the parameter for the delegate with a parameter name of AsyncCallback.

For more information on invoking XML Web services asynchronously, see [<topic://cpconInvokingWebServicesAsynchronously>].

Namespace: System.Web.Services.Protocols
Assembly: System.Web.Services (in System.Web.Services.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0