In the previous chapters, we created a basic WCF service. The WCF service we have created, HelloWorldService, has only one method, named GetMessage. As this was just an example, we implemented this WCF service in one layer only. Both the service interface and implementation are within one deployable component.

In the following two chapters, we will implement a WCF service, which will be called LayerNorthwindService, to reflect a real-world service. In this chapter, we will separate the service interface layer from the business logic layer, and in the following chapter, we will add a data access layer to the service.

Note that the service we will create in the next two chapters is only a simplified version of a real-world WCF service. In a real-world situation, there is no doubt that the WCF service will contain more custom scenarios, business logic, and data constraints. For learning purposes, we will just create a WCF service in three layers...