ASP.NET Developer's JumpStart By Paul D. Sheriff, Ken Getz
Table of Contents
Part IV. Web Services
Compare synchronous and asynchronous calls to Web Service methods
Learn to create the required procedure for callbacks in order to call a Web Service asynchronously
When you create a client application that consumes a method from a Web Service, most likely your application simply calls a method in the object provided by the Web Service or so it would seem. Your code doesn't actually call a method in some remote object that wouldn't make any sense. Under the covers, your code is calling a method in a local object that knows how to contact the remote Web Service and execute the method using SOAP. This local object then retrieves a return value from the remote Web Service method and returns that value back to you.
In this chapter, you'll first create an XML Web Service consumer that calls the method of the Web Service synchronously, much as you might have done previously. Then, you'll learn how to call a Web Service method asynchronously. This allows your application to return immediately after calling the method and await the results while accomplishing other tasks.