What are the various ways of accessing a web service?

Asynchronous Call : Application can make a call to the Webservice and then continue todo watever oit wants to do. When the service is ready it will notify the application. Application can use BEGIN and END method to make asynchronous call to the webmethod. We can use either a WaitHandle or a Delegate object when making asynchronous call.
The WaitHandle class share resources between several objects. It provides several methods which will wait for the resources to become available
The easiest and most powerful way to to implement an asynchronous call is using a delegate object. A delegate object wraps up a callback function. The idea is to pass a method in the invocation of the web method. When the webmethod has finished it will call this callback function to process the result
Synchronous Call : Application has to wait until execution has completed.