There are 3 message exchange patterns (MEP) in the WCF: Request/Response , One Way and Duplex - I'm going to talk about Duplex pattern in this post. In duplex pattern Both the client and the server can send messages to each other independently. This can be used by request/Response messaging pattern too but In the request/Response and one-way message exchange patterns, the communication is initiated by the client application, but in the duplex message exchange pattern, both the...