Overloading Controller Methods in a MVC Project

I cranked up a new MVC3 project (Razor and Unit Testing). I went to the Home controller and added an overloaded method to the Index:

        public ActionResult Index(string userName)
        {
            ViewBag.Message = String.Format("Welcome to ASP.NET MVC, {0}!", userName);
            return View();
        }

I then hit F5 and got the following error:

I tried adding a route:

            routes.MapRoute(
                "HomeIndexWithString", 
                "Home/Index/{userName}", 
                new { controller = "Home", action = "Index", userName = "" } 
            );

and being explicit with the URL but I got the same error:

I then looked on Stack Overflow and added the ActionName attribute to my overloaded method:

        [ActionName("HomeIndexWithString")]
        public ActionResult Index(string userName)
        {
            ViewBag.Message = String.Format("Welcome to ASP.NET MVC, {0}!", userName);
            return View();
        }

The Index page returned, but the problem is that even when I passed in the explicit url, it still returned the default page. I then went back to the overloaded method and deleted it. I then added an optional parameter to the original index method and handled it if the value was populated:

        public ActionResult Index(string? userName)
        {
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.Append("Welcome to ASP.NET MVC");
 
            if (userName != null)
            {
                stringBuilder.Append(String.Format(", {0}!", userName));
            }
            ViewBag.Message = stringBuilder.ToString();
            return View();
        }

The problem is that the compiler complains:

Error 1 The type ‘string’ must be a non-nullable value type in order to use it as parameter ‘T’ in the generic type or method ‘System.Nullable<T>’

So I am down to creating a custom ActionMethodSelectAttribute that can handle the requests and parse appropriately. Since this smells like a kludge, I went back to the way MSFT wants me to do it – create a different method for each action and return to appropriate view. Naming confusion notwithstanding, I guess that is what I will do…