title: How to prioritize Web Api Controllers over IHttpHandler?
body: <p>I have a legacy project that has a single IHttpHandler implementing class that routes all the requests using a huge switch statement etc.. I am trying to introduce Attribute Routing with ApiControllers but the first one always has the priority. Is it possible to configure the system (either code or IIS) so that Web ApiControllers have priority over my single IHttpHandler implementing class? In IIS, I put my AttributeRouting first and then there are all the aspx ones but still the Web Api Controller is not getting processed first..no matter what I do (having them under the same project). I don't want to introduce a separate project.</p>
  
  <p><strong>Edit:</strong> There is a IHttpModule that decides based on what is after api/ to route it to specific ashx file. One of them is the one described..</p>
  
  <p><strong>Edit 2:</strong> More specifically: If the uri doesn't have a list of filtered things [file,message,property ...] it is routed to Resource.aspx</p>
  
  <p>so api/file, api/message, api/property would be handle from other .ashx files - otherwise the traffic goes to Resource.ashx...</p>
  
  <p>As a result the requests that have api/endpoint1, api/endpoint2, api/endpoint3 
  will all go to Resource.aspx. The question is how to route api/endpoint3 to the API Controller described below.
  Thanks</p>
  
  <p>Simplified Code Architecture:</p>
  
  <pre><code> //SolutionName/Api/MyModule.cs (Legacy Code)
   //this routes based on what is after api/ to Resource.ashx or other ashx files
   public class MyModule : IHttpModule {
      //if url doesn't contain [file,message,property ...] route to Resource.ashx
   }
  </code></pre>
  
  <hr>
  
  <pre><code>//SolutionName/API/Resource.ashx (Legacy Code)
  //this is hit at any request solutionname/api/anything
  public class DefaultHandler : IHttpHandler 
  {
     public void ProcessRequest(HttpContext context) {
         String APIBranch = parse(context);
         switch(APIBranch)
         {
             case "endpoint1": methodOne(); break;
             case "endpoint2": methodTwo(); break;
             [...]
             default: throw Exception(); break;
         }
     }
  }
  </code></pre>
  
  <hr>
  
  <pre><code>//SolutionName/API/App_Start/AttributeRoutingHttpConfig.cs
  public static class AttributeRoutingHttpConfig
  {
      public static void RegisterRoutes(HttpRouteCollection routes) 
      {    
          // See http://github.com/mccalltd/AttributeRouting/wiki for more options.
          // To debug routes locally using the built in ASP.NET development server, go to /routes.axd
  
          routes.MapHttpAttributeRoutes();
      }
  
      public static void Start() 
      {
          RegisterRoutes(GlobalConfiguration.Configuration.Routes);
      }
  }
  </code></pre>
  
  <hr>
  
  <pre><code>//SolutionName/API/Controllers/MyController.cs
  //this should have been hit for a GET on solutionname/api/endpoint3/id
  [RoutePrefix("endpoint3")]
  public class MyController : ApiController
  {
      private IModelDao modelDao;
  
      MyController(IModelDao modelDao){
          this.modelDao = modelDao;
      }   
  
      [Route("{id}")]
      [HttpGet]
      public Model GetSomething(int id)
      {
          Model model = modelDao.GetSomething(id);
          return model;
      }
  }
  </code></pre>