Programming WCF Services

Per-Session Services

WCF can maintain a session between a client and a particular service instance. When the client creates a new proxy to a service configured as a sessionful service, the client gets a new dedicated service instance that is independent of all other instances of the same service. That instance will remain in service usually until the client no longer needs it. This activation mode is very much like the classic client-server model. This mode is also sometimes referred to as private sessions. Each private session uniquely binds a proxy and its set of client- and service-side channels to a particular service instance (actually to its context, as discussed later on).

Because the service instance remains in memory throughout the session, it can maintain state in memory, and the programming model is very much like that of the classic client/server. Consequently, it also suffers from the same scalability and transaction issues as the classic client/server model. A service configured for private sessions cannot typically support more than a few dozen (or perhaps up to a hundred or two) outstanding clients due to the cost associated with each such dedicated service instance.

Tip

The client session is per service endpoint per proxy. If the client creates another proxy to the same or a different endpoint, that second proxy will be associated with a new instance and session.

Configuring Private Sessions

Supporting a session has three elements to it—behavior, binding, and contract. ...