Route not working - ASP.NET MVC 3 Localization locale in URL - asp.net-mvc

Question

I am localizing my MVC3 site based on the route data. for example, http://domain/fr should display the site in French and http://domain should default to english...below is how i registered my routes in Global.ascx.
My issue is that http://domain/fr/Home/Index will work, but http://domain/Home/Index will display resource not found error, and with an investigation it tells me the route table is mapping "Home" to {lang}
What am I missing?
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.IgnoreRoute("favicon.ico");
routes.MapRoute(
"LogOn", // Route name
"Account/{action}", // URL with parameters
new { controller = "Account", action = "LogOn" } // Parameter defaults
);
routes.MapRoute(
"Localization", // Route name
"{lang}/{controller}/{action}", // URL with parameters
new { UrlParameter.Optional, controller = "Home", action = "Index"} // Parameter defaults
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}", // URL with parameters
new { controller = "Home", action = "Index"} // Parameter defaults
);
}

Answer 1

routes.MapRoute(
"Default", // Route name
"{controller}/{action}", // URL with parameters
new { controller = "Home", action = "Index"}, // Parameter defaults
new { controller = "[a-zA-Z]{3,}" } //regexp constraint on controller name
);
routes.MapRoute(
"Localization", // Route name
"{lang}/{controller}/{action}", // URL with parameters
new { UrlParameter.Optional, controller = "Home", action = "Index"} // Parameter defaults
);
Should do the trick, provided all your controller names are longer than 2 characters :)