How to Create a Web Service with .NET

You hear all about Web Services but do you know how to create one? In this simple "How To" paper, we will try to demonstrate how to write and deploy a simple Web Service using Microsoft’s .NET environment with Visual Basic attend this session, and go back home very dangerous! 1. What is a Web Service? Simply stated, a Web Service offers a method (or methods) that can be invoked using open standards (including HTTP and XML) for communication. For those readers who are not up to speed on object-oriented programming, a method is just a function or procedure that is associated with an object. In other words, when a method is invoked, it simply executes an action of some kind. Web services are interesting because they offer a way to create programs that are platform-independent. These programs are accessed over the Web independent of the tools used to create them and the operating system they run on. Another characteristic of a Web service is that it must supply discovery information about itself. This means that you can query a Web service and have it tell you the names of the methods it provides, the arguments accepted by each method, and the return values for the methods. In other words, you don’t have to know very much about a Web service other that it exists to be able to use it in your programs. The driving force is that Web services are to provide components that can communicate with each other regardless of the language they were written in, and regardless of the operating system on which they run. Web services make their methods available for use or consumption, by other programs. To consume a Web service, a program makes a request running over HTTP to use the methods available via HTTP GET and HTTP POST – or more commonly – Simple Object Access Protocol (SOAP). Microsoft’s .NET environment insulates the Web service developer from the coding details of SOAP. With respect to the universal discovery mechanism provided by Web services, .NET automatically creates a Web Services Discovery Language (WSDL) document, which other applications (or people!) can read to understand how to use the Web service. Again, .NET insulates the developer from the details of creating the WSDL document, so it is important to know that it exists. Web services also make use of Universal Description, Discovery, and Integration (UDDI). UDDI is a kind of Yellow Pages for Web services, and you need to use UDDI to find a Web service, or if you want to make sure that your Web service can be found.