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The Basic Composition of a WCF Application

When you are building a WCF distributed system, you will typically do so by creating three interre-

lated assemblies:

•

The WCF Service assembly: This *.dll contains the classes and interfaces that represent the

overall functionality you are exposing to external callers.

•

The WCF Service host: This software module is the entity that hosts your WCF service assembly. 

•

The WCF client: This is the application that accesses the service’s functionality through an

intervening proxy.

As mentioned, the WCF service assembly is a .NET class library that contains a number of WCF

contracts and their implementations. The one key difference is that the interface contracts are

adorned with various attributes that control data type representation, how the WCF runtime inter-

acts with the exposed types, and so forth. 

The second assembly, the WCF host, can literally be any .NET executable. As you will see in this

chapter, WCF was set up in such a way that services can be easily exposed from any type of applica-

tion (Windows Forms, a Windows service, WPF applications, etc.). When you are building a custom

host, you will make use of the ServiceHost type and a related *.config file, which contains details

regarding the server-side plumbing you wish to make use of. However, if you are using IIS as the

host for your WCF service, there is no need to programmatically build a custom host, as IIS will

make use of the ServiceHost type behind the scenes.