How Your WCF Service Can Use MSMQ as a Durable Message Store

y previous DevX article "WCF and MSMQ—Take a Message" explained the benefits of introducing queues into an application architecture. Queues provide a useful isolation layer between a service and a caller (or vice-versa) and become a place for messages to live while waiting to be processed. To summarize that article, when queues are used properly they can:

• Increase application robustness, because clients can send messages even when services are not running
• Increase application scalability, as multiple service instances can be used to process messages from a single queue
• Improve client responsiveness, thus eliminating the need for clients to wait on a response from the service
• Reduce dependencies between client and services, because all communication is indirect via queues
• Ensure the durability of messages, because they can survive service and system failures

Through the MsmqIntegrationBinding and NetMsmqBinding bindings, Windows Communication Foundation (WCF) has baked-in integration with Microsoft Message Queuing (MSMQ), which makes building applications simple. The following are the two solutions for which you can utilize the integration between WCF and MSMQ:

1. A WCF client application can communicate with an existing MSMQ-based application using the MsmqIntegrationBinding binding. In essence, a WCF-based client can be used to place messages directly into an MSMQ queue. The client can then be processed by another application (referred to hereafter as a service for the sake of simplicity).
2. A WCF service or client can use an MSMQ queue as a message store via NetMsmqBinding. The WCF endpoints are unchanged; the key differentiator being messages are placed into queues to await processing rather than being sent directly into the WCF runtime.