Does MVC routes look for pattern or names - asp.net-mvc

Question

I am trying to understand routes, but am very confused.
The question is simply, does the default values have any impact on which router is chosen, or is it simply the pattern.
For example, consider the following
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{startIndex}",
defaults: new { controller = "Home", action = "Index", startIndex = UrlParameter.Optional }
);
routes.MapRoute(
name: "About",
url: "{controller}/{action}/{startIndex}",
defaults: new { controller = "About", action = "Index", startIndex = UrlParameter.Optional }
);
Regardless of whether the end result is the same, would MVC simply choose the first every time since the URL: pattern matches the request, and therefore ignore that they have different controllers?

Answer 1

Route selection uses pattern matching and will select the first matching pattern. In your example, there's no reason for your second route as the first will match /about/... as well as the second and result in the same action being invoked. If you need to have routes which have the same basic pattern, perhaps the values in the pattern affect the controller you use, you can use routing constraints to aid in choosing the correct route or use fixed values and place the route before the default route.
routes.MapRoute(
name: "Contact",
url: "/contact",
defaults: new { controller = "about", action = "contactus", id = "" }
);
routes.MapRoute(
name: "Help",
url: "/help",
defaults: new { controller = "about", action = "help", id = "" }
);
routes.MapRoute(
name: "Admin",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Admin", action = "Index", id= UrlParameter.Optional },
constraints: new { controller = "(admin)|(orgadmin)" }
);
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{startIndex}",
defaults: new { controller = "Home", action = "Index", startIndex = UrlParameter.Optional }
);