Correct 404 message for a missing ASP.Net MVC controller

Question

I have an MVC 2 application that should always give a \'nice\' 404 page.

However currently I get a low level .Net one: \"Server Error in \'/sitename\' Applicatio

Answer 1

I finally found the answer to this, though it's still not ideal.

You can restrict the controller names that are allowed to match a route using a regex, so if we assume the default implementation of the controller factory we can figure out all the possible class names that are supported:

// build up a list of known controllers, so that we don't let users hit ones that don't exist
var allMvcControllers = 
    from t in typeof(Global).Assembly.GetTypes()
    where t != null &&
        t.IsPublic &&
        !t.IsAbstract &&
        t.Name.EndsWith("Controller", StringComparison.OrdinalIgnoreCase) &&
        typeof(IController).IsAssignableFrom(t)
    select t.Name.Substring(0, t.Name.Length - 10);

// create a route constraint that requires the controller to be one of the reflected class names
var controllerConstraint = new
{
    controller = "(" + string.Join("|", allMvcControllers.ToArray()) + ")"
};

// default MVC route
routes.MapRoute(
    "MVC",
    "{controller}/{action}/{id}",
    new { action = "Index", id = UrlParameter.Optional },
    controllerConstraint);

// fall back route for unmatched patterns or invalid controller names
routes.MapRoute(
    "Catch All", 
    "{*url}",
    new { controller = "System", action = "NotFound" });

This isn't ideal, it adds a hit on the application start and still feels far too complicated, but it does have the desired effect.