ASP.NET MVC3 and 404’s for Area Controllers

So I’m a big fan of ASP.NET MVC, and the general idea of convention over configuration, but I spent a few hours late last night fighting with something, and the Google was no help, so hopefully this helps someone else…

The situation:

I have ASP.NET MVC3 project, and I created an Area for my json API.  In my area I create a simple controller called CategoriesController, and I registered some routes in my AreaRegistration…

//handles get for a list of all categories
context.MapRoute(
    "ListCategories",
    "API/Categories",
    new { controller = "Categories", action = "List" }
);

I used the very awesome MvcRouteUnitTester (on Nuget) to write unit tests to make sure this route was working. All systems go!

Before I started writing tests against the actual controller, I used a browser to hit http://localhost/myapp/API/Categories – which should match this route, and spit back some “hello world” json. I get a 404.

Even with the unit tests, I decided to pull in the RouteDebugger NuGet package, just to make sure that the routes were working, and that showed that all was good

So, I’m stumped. No Exceptions, everything seems to line up, but still a 404.

After about 15 minutes of useless Googling, I remember that I’ve got logging setup in this project, and that’s in my Global.asax.cs and tied into Application_Error…

protected void Application_Error()
{
    Exception lastException = Server.GetLastError();
    var logger = DependencyResolver.Current.GetService<ILogger>();
    logger.Fatal(lastException);
}

SO I look in the log… and find this error

The controller for path ‘/statsme/API/Categories/List’ was not found or does not implement IController.

(full trace because this will help Google index this when others go lookin)…

Message :The controller for path '/statsme/API/Categories/List' was not found or does not implement IController.
Source :System.Web.Mvc
Stack Trace :   at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType)
   at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName)
   at System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<BeginProcessRequest>b__2()
   at System.Web.Mvc.SecurityUtil.<>c__DisplayClassb`1.<ProcessInApplicationTrust>b__a()
   at System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust[TResult](Func`1 func)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
TargetSite :System.Web.Mvc.IController GetControllerInstance(System.Web.Routing.RequestContext, System.Type)

Ok, WTF? CategoriesController inherits from a BaseController which inherits from Controller, so we’re clear on the IController bit. I know the class is there… what is going on?

Google… Google… more Google. Random hacking… cursing… Ah HA!

The issue was the namespace on my controller. Turns out that MVC has a convention that the area name is expected to be in the namespace of the controller.

So – I had StatsMe.API.CategoriesController, but MVC was looking for StatsMe.Areas.API.CategoriesController.

What finally tipped me off was some stuff in the RouteDebugger output…

Annoying because the error message really could have helped out by saying “Hey – I’m looking for StatsMe.Areas.API.CategoriesController and I can’t find it”, rather than the very generic message it spit out.

Configuration Overriding Convention

As we all know, in MVC where there is a convention, there is a way to override this, and that’s in the route definition… like so…

context.MapRoute(
    "ListCategories",
    "API/Categories",
    new { controller = "Categories", action = "List" },
    new[] { "StatsMe.API.Controllers" }
);

Viola! Hope this helps someone else avoid a few hours of frustration.