Programming Visual Basic .NET, Second Edition

Chapter 16. Programming Web Services

.NET Web Services expand on the concept of distributed processing to build components whose methods can be invoked across the Internet. These components can be built in any .NET language, and they communicate using open protocols that are platform-independent.

For example, a stock exchange server might provide a web service method that takes a stock ticker symbol as a parameter and returns a quote. An application might combine that service with another service from a different company that also takes a stock symbol but that returns background data about the company. The application developer can concentrate on adding value to these services, rather than duplicating the same service for his own application.

The list of web services that might be useful to developers and end users seems boundless. A bookstore might provide a web service that takes an ISBN and returns the price and availability of a title. A hotel’s web service might take a date range and number of guests and return a reservation. Another web service might take a telephone number and return a name and address. Yet another might provide information about the weather or shuttle launches.

In such a world, a single application might draw on and stitch together the services of hundreds of small web services distributed all over the world. This takes the Web to an entirely new dimension: not only is information retrieved and exchanged, but also methods are invoked and applications are ...