Programming WCF Services

Endpoints

Every service is associated with an address that defines where the service is, a binding that defines how to communicate with the service, and a contract that defines what the service does. This triumvirate governing the service is easy to remember as the ABC of the service. WCF formalizes this relationship in the form of an endpoint. The endpoint is the fusion of the address, contract, and binding (see Figure 1-5).

Figure 1-5. The endpoint

Every endpoint must have all three elements, and the host exposes the endpoint. Logically, the endpoint is the service’s interface, and is analogous to a CLR or COM interface. Note in Figure 1-5 the use of the traditional “lollipop” to denote an endpoint.

Tip

Conceptually, even in C# or VB, an interface is an endpoint: the address is the memory address of the type’s virtual table, the binding is CLR JIT compiling, and the contract is the interface itself. Because in classic .NET programming you never deal with addresses or bindings, you take them for granted. In WCF the address and the binding are not ordained, and need to be configured.

Every service must expose at least one business endpoint and each endpoint has exactly one contract. All endpoints on a service have unique addresses, and a single service can expose multiple endpoints. These endpoints can use the same or different bindings and can expose the same or different contracts. There ...