How can I avoid duplicate content in ASP.NET MVC due to case-insensitive URLs and defaults?

Question

Edit: Now I need to solve this problem for real, I did a little more investigation and came up with a number of things to reduce duplicat

Answer 1

Bump!

MVC 5 Now Supports producing only lowercase urls and common trailing slash policy.

    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.LowercaseUrls = true;
        routes.AppendTrailingSlash = false;
     }

Also on my application to avoid duplicate content on different Domains/Ip/Letter Casing etc...

http://yourdomain.com/en

https://yourClientIdAt.YourHostingPacket.com/

I tend to produce Canonical Urls based on a PrimaryDomain - Protocol - Controller - Language - Action

public static String GetCanonicalUrl(RouteData route,String host,string protocol)
{
    //These rely on the convention that all your links will be lowercase! 
    string actionName = route.Values["action"].ToString().ToLower();
    string controllerName = route.Values["controller"].ToString().ToLower();
    //If your app is multilanguage and your route contains a language parameter then lowercase it also to prevent EN/en/ etc....
    //string language = route.Values["language"].ToString().ToLower();
    return String.Format("{0}://{1}/{2}/{3}/{4}", protocol, host, language, controllerName, actionName);
}

Then you can use @Gabe Sumner's answer to redirect to your action's canonical url if the current request url doesn't match it.