The Framework always tries to match the URL of the request to a route
in the order of the Routes added to the RouteCollection
So you should put the custom routes before the default route,
//Custom route
routes.MapRoute(
name: "Contact",
url: "Contact",
defaults: new { controller = "Home", action = "Contact" }
);
//default route
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);