ASP.NET MVC Subdomain Routing

RouteConfig.cs

public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            routes.MapRoute(
                    "Sub", // Route name
                    "{controller}/{action}/{id}", // URL with parameters
                    new { controller = "SubdomainController", action = "AnyActionYouLike", id = UrlParameter.Optional },
                    new { controller = new SubdomainRouteConstraint() },
                    new[] { "MyProjectNameSpace.Controllers" }
                    );

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
            );
            
        }
    }

SubdomainRouteConstraint.cs

public class SubdomainRouteConstraint : IRouteConstraint
    {
        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values,
                          RouteDirection routeDirection)
        {
            string url = httpContext.Request.Headers["HOST"];
            int index = url.IndexOf(".", System.StringComparison.Ordinal);

            if (index < 0)
            {
                return false;
            }
            
            string sub = url.Split('.')[0];
            if (sub == "www" || sub == "yourdomainname" || sub == "mail" /* || sub = "some-blacklist-subdomain" */)
            {
                return false;
            }

            //Add a custom parameter named "user". Anythink you like :)
            values.Add("subdomainAsAParameter", sub);
            return true;
        }
    }

How can i use this ? are there any project for this ?
Please give any one example.

I have created one project and creating multiple subdomain based on our requirement.

Hi,
I am trying to create sub directory base on ip address,
For example, my current website is www.nextan.biz, as my company expending business to following countryies, Australia, Singapore and Japan. So, i want to create url likes

www.nextan.biz/au/
www.nextan.biz/sg/
www.nextan.biz/jp/

I tried, to modify

routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "welcome", action = "Index", id = UrlParameter.Optional}
);

routes.MapRoute(
name: "LocalizedDefault",
url: "{countrycode}/{controller}/{action}/{id}",
defaults: new { controller = "welcome", action = "Index", id = UrlParameter.Optional },
constraints: new { countrycode = "sg" }
);

countrycode - will change base on the client IP Address, but it is not working for me.

can you please help me to share some ideas.

Thank you