In this chapter, we built a simple WCF application and decomposed it into its major components at run time. We saw that the application developer-facing WCF API is fairly straightforward but still offers considerable flexibility to the application developer. We also saw that the addresses, bindings, contracts, and behaviors that give WCF its simple API are used by two major architectural layers: the ServiceModel layer and the Channel layer. The remainder of this book covers both of these layers in detail.