Asynchronous Web Services
Note: Paul Kimmel is a private pilot. He finished his flight training at Canelas Internation Aviation, Inc. in Austin, Texas, and is a partner in Spartan Wings, a flying club in the greater Lansing, Michigan area.
Asynchronous programming is a valuable technique. Asynchronously call a method that you suspect will take some time, and the called method will immediately returneven though it probably hasn't finished. Perform some additional work, and when the asynchronously called method has completed the request it will call you back. Instead of waiting for a long call, you can perform some work in the meantime. This is like flipping your eggs and pouring your morning juice while the toaster is browning the bread, as opposed to hovering over the toaster before cooking the eggs or squeezing the juice.
The same asynchronous capabilities afforded to Windows programming is extended to Web Services.
This article assumes that you have a basic understanding of Web Services. For example, you know how to create, find, and call web methods, or you have handy a copy of a book such as Visual Basic .NET Unleashed (Sams, 2002, ISBN 0-672-32234-X), which answers fundamental questions about related topics such as UDDI, WSDL, and attributes.