Why do you need to specify the controller and action in the default route for the RoutesTable in ASP.NET MVC?

Question

Why do we have to specify the defaults for the default route?

This is a normal default route:

  routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
  );

Why can't I just do this:

  routes.MapRoute(
        name: "Default",
        url: "Home/Index/{id}",
        defaults: new {id = UrlParameter.Optional } 
  );

I already specified the action and controller but when I use this way, I get an error. Does anyone know why you have to specify the action and controller in the default route?

Answer 1

Without a default set of parameters, how is routing supposed to know where to send this URL?

/

The defaults let you do that URL, so it knows to use the 'Home' controller's 'Index' method.

Or:

/Articles

In this case, the 'Index' action of the 'Articles' controller would be called. Without those defaults, again, routing has no way to know what to do.