While I was working on ELMAH.MVC v.2.0.0 I noticed a something that contradicts the way I understand how the controller resolving mechanism works. Before, I always thought that namespaces matters, but in practice I saw otherwise.

Controller in separate class assembly

The good way of distributing re-usable software is class assembly. Suppose, I have 2 projects - one ASP.NET MVC web application (MvcApplication2), and another one that is a class assembly (Awesome.Mvc.Lib). Web application references the class library.

I want to have some particular controller to be exposed from Awesome.Mvc.Lib. Namely, I want to have a controller inside the class library, that would be accessible from MvcApplication2. I'll add some ShinnyController.cs inside.

namespace Awesome.Mvc.Lib
{
    public class ShinnyController : Controller
    {
        [HttpGet]
        public string Index()
        {
            return "I'm in Shinny controller";
        }
    }
}  

Originally, my thought was, ShinnyController will always be "invisible" for MvcApplication2, since it placed into another namespace. Meaning, if I don't initialize a route pointing to ShinnyController, the routing mechanisms would never match it. But, if I run the application and go http://localhost:26810/shinny I will see:

This is totally unexpected to me! It turns out that default route is matching the controller/action from Awesome.Mvc.Lib class library.

routes.MapRoute(
    "Default", // Route name
    "{controller}/{action}/{id}", // URL with parameters
    new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);

What I'm expecting though is that ShinnyController.cs have to be "explicitly" routed, and ideally placed into its own sub-URL, like http://localhost:26810/awesome/shinny.

What about namespaces fallback?

I've asked this question on stackoverflow. Even if I had good answer, it did not make it happy. So, to get the behavior I want, I need to do the following:

1. Change the default routing to explicitly mention the namespace and set fallback to false:

public class MvcApplication : System.Web.HttpApplication
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
 
        var route = routes.MapRoute(
            "Default", // Route name
            "{controller}/{action}/{id}", // URL with parameters
            new { controller = "Home", action = "Index", id = UrlParameter.Optional }, // Parameter defaults
            new[] { "MvcApplication2" }
        );
 
        route.DataTokens["UseNamespaceFallback"] = false;
 
    }

      2.   Create an Area in Awesome.Mvc.Lib and configure routing to it:

public class AwesomeAreaRegistration : AreaRegistration
{
    public override void RegisterArea(AreaRegistrationContext context)
    {
        context.MapRoute("Awesome_default", "Awesome/{controller}/{action}", new { action = "Index" });
    }
 
    public override string AreaName
    {
        get { return "Awesome"; }
    }
}

After I did so, I can reach the http://localhost:26810/awesome/shinny:

And in the same time, http://localhost:26810/shinny is getting to be rejected:

Even though, it looks like desired behavior.. It sucks.

Why it sucks?

By placing the controllers into separate assembly, I'm thinking about it's distribution by simple bin-deployment or by Nuget. Both ways assumes, simple copy of assembly into particular location, adding references and that's it! I don't suppose to change default routing that comes in ASP.NET MVC applications templates.

I want to have the control of routes *inside* the class library, not outside of it (in web application). But, the default behavior of ASP.NET MVC routing is completely different. Moreover, in some cases I want users of library to be able to control the routing.

In my opinion the default behavior with UseNamespaceFallback = true is wrong. I'll give one more example, to prove it.

I removed namespace fallback code from default route, after added new Area, called Api. Inside this Area I place one controller, called SimpleController.

namespace MvcApplication2.Areas.Api.Controllers
{
    public class SimpleController : Controller
    {
        public string Index()
        {
            return "I'm simple controller from API area";
        }
 
    }
}

The controller is reachable, as expected:

But now, I try to access /simple:

Hey WTF? The whole idea of Areas is just ruined. What am I doing wrong?

I'm feeling very frustrated about this issue. Even though I understand why it happens, it smells like a bug for me? It works exactly the same for ASP.NET MVC 2, 3, 4. I'm asking you guys, to help to clarify the problem. What is your opinion on that? Do you agree on such default behavior?