Chapter 4.4. WebServices

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IN THIS CHAPTER

• Echo Service

• Returning User-Defined Types

• XML Attributes

Accessing data with distributed applications has produced various technologies over the years . From general Remote Procedure Calls (RPC) mechanisms, such as XML-RPC, to full-blown distributed objects, such as CORBA and DCOM. The WebServices paradigm is based on the simple premise of extending the basic XML-RPC mechanism to allow for procedure calls over the Internet using open transport protocols such as HTTP over TCP/IP connections.

.NET supports WebServices invocations through HTTP POST, HTTP GET, and Simple Object Access Protocol (SOAP). Before the introduction of WebServices support in .NET, developing a WebService host, proxy, and client was a non-trivial task. Microsoft even released a SOAP Toolkit for Visual Studio 6 that allowed a developer to expose a COM object over the Internet. This Toolkit falls short of the support offered by .NET and C#. Developing a WebService requires little more than defining a public set of methods to expose to clients , along with the proper return types and applying simple WebMethodAttributes to those methods.

In the course of this chapter, a small EchoService will serve as the starting point to familiarize you with the concept of WebService s and eventually a WebService interface will be added to the EmployeeBrowser ASP WebApplication .

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