Creates the context specified by the ServiceConfig object and pushes it onto the context stack to become the current context.
Assembly: System.EnterpriseServices (in System.EnterpriseServices.dll)
first creates a context configured as specified by the ServiceConfig object that is passed as the cfg parameter. Policies on both the client and server sides are then triggered as if a method call had occurred. The new context is then pushed onto a context stack and becomes the current context. Because of their efficient design and because no thread marshaling is involved, using and Leave involves significantly reduced overhead compared to an equivalent method call.