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PORefactoring "procedural" WCF service
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copied!<p>I'm tryng to refactor a monstrous WCF service into something more manageable. At the time of writing, the service takes about 9 dependencies via constructor, which makes unit testing it very difficult.</p> <p>The service is handling local state via state machine, does validation on the parameters, throws fault exceptions, performs the actual operation and fires publication events via a pub/sub channel. This code is very similar accross all other service calls.</p> <p>I realize that I can do several of those things (argument validation, pub/sub notifications) differently, perhaps via <a href="http://en.wikipedia.org/wiki/Aspect-oriented_programming" rel="noreferrer">Aspect-Oriented Programming</a> or WCF behaviors, but my gut tells me that the general approach is wrong -- this feels too "procedural".</p> <p>My goal is to separate the execution of the actual operation from things like pub/sub notifications, and perhaps even error handling.</p> <p>I wonder if acronyms like <a href="http://en.wikipedia.org/wiki/Domain-driven_design" rel="noreferrer">DDD</a> or <a href="http://martinfowler.com/bliki/CQRS.html" rel="noreferrer">CQRS</a> or other techniques can help out here? I am, unfortunately, not very familiar with those concepts beyond the definition.</p> <p>Here's a (simplified) example of one such WCF operation:</p> <pre><code>public void DoSomething(DoSomethingData data) { if (!_stateMachine.CanFire(MyEvents.StartProcessing)) { throw new FaultException(...); } if (!ValidateArgument(data)) { throw new FaultException(...); } var transitionResult = _stateMachine.Fire(MyEvents.StartProcessing); if (!transitionResult.Accepted) { throw new FaultException(...); } try { // does the actual something DoSomethingInternal(data); _publicationChannel.StatusUpdate(new Info { Status = transitionResult.NewState }); } catch (FaultException<MyError> faultException) { if (faultException.Detail.ErrorType == MyErrorTypes.EngineIsOffline) { TryFireEvent(MyServiceEvent.Error, faultException.Detail); } throw; } } </code></pre>

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