Professional C# 4 and .NET 4

Chapter 55. Web Services with ASP.NET

WHAT'S IN THIS CHAPTER?

• The syntax of SOAP and WSDL

• How SOAP and WSDL are used by web services

• Exposing and consuming web services

• The use of web services

• Exchanging data by using SOAP headers

Web services are a way of performing remote method calls over HTTP that can make use of Simple Object Access Protocol (SOAP). In the past, this issue was fraught with difficulty, as anyone who has any DCOM (Distributed COM) experience knows. Using older technologies, the act of instantiating an object on a remote server, calling a method, and obtaining the result is far from simple, and the necessary configuration is even trickier.

SOAP simplifies matters immensely. This technology is an XML-based standard that details how method calls can be made over HTTP in a reproducible manner. A remote SOAP server is capable of understanding these calls and performing all the hard work for you, such as instantiating the required object, making the call, and returning a SOAP-formatted response to the client.

The .NET Framework makes it very easy for you to do this. As with ASP.NET, you are able to use the full array of C# and .NET techniques on the server, but (perhaps more importantly) the simple consumption of web services can be achieved from any platform with HTTP access to the server. In other words, it is conceivable that Linux code could, for example, use ASP.NET web services, or even Internet-enabled fridges. To quote a real-world example, in the past I have had great ...