Summary

Asynchronous calls should be used when a synchronous call would leave an application waiting for an extended amount of time. The .NET Framework allows Web Services to be called asynchronously without any additional work on the part of the Web Service developers. Web Services can be called asynchronously while specifying a callback method to be executed when the asynchronous call completes, or the application can “wait” for the execution to complete. The consumer of the Web Service can decide how long to wait for an asynchronous Web Service method to complete execution and whether to cancel the execution. If the response may take a long time to return, the request and response can be completely disconnected. In this situation, both the client and the server need to implement a Web Service and provide a mechanism to map requests and responses.