This chapter is based on a case study named ShoppingAssistant, which provides one stop shopping for
consumers that want to find out information such as the products that are on sale, availability of prod-
ucts in different stores, comparison of the price of the product across different stores and so on. In this
case study, I demonstrate how to leverage Web services in a real world Web application by using asyn-
chronous Web service invocation capabilities in conjunction with other .NET features such as XML
Serialization, FileSystemWatcher, and Timer component.
you can learn xml at here