title: ASP.NET WebAPI - How to scan registered Actions
body: <p>I have several methods in my WebApi which return HttpResponseMessage. As the response type is unknown, I have to register them in HelpPageConfig using something like </p>
  
  <p><code>config.SetActualResponseType(typeof(X), "SomeController", "GetX");
  </code></p>
  
  <p>I would like to register these using a custom attribute <code>[ActualResponse(typeof(X)]</code> where the controller is declared to avoid creating a large registry object which references everything in a bit messy list.</p>
  
  <p>How can I interrogate the config in order to get a list of the registered controllers and actions and their attributes so that I can call SetActualResponseType automatically?</p>