Create Route for a specific URL without changing the URL with MVC

Question

I have a MVC Web Application that runs on www.domain.com and I need to configure a different URL binding for another domain www.domain2.com for the same web application.

The new domain www.domain2.com will have to return a specific Controller Action View like /Category/Cars:

routes.MapRoute(
    name: "www.domain2.com",
    url: "www.domain2.com",
    defaults: new { controller = "Category", action = "Cars", id = UrlParameter.Optional }
);

How can I achieve this without changing the URL, so the visitor inserts the url www.domain2.com and receives the view www.domain.com/category/cars but the url remains www.domain2.com?

EDIT:

I have tried this approach but it's not working:

routes.MapRoute(
    "Catchdomain2",
    "{www.domain2.com}",
    new { controller = "Category", action = "Cars" }
);

Answer 1

Domains are normally not part of routes, which is why your examples don't work. To make routes that work only on specific domains you have to customize routing.

By default, all of the routes in your route configuration will be available on all domains that can reach the web site.

The simplest solution for this is to create a custom route constraint and use it to control the domains that a specific URL will match.

DomainConstraint

    public class DomainConstraint : IRouteConstraint
    {
        private readonly string[] domains;

        public DomainConstraint(params string[] domains)
        {
            this.domains = domains ?? throw new ArgumentNullException(nameof(domains));
        }

        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
        {
            string domain =
#if DEBUG
                // A domain specified as a query parameter takes precedence 
                // over the hostname (in debug compile only).
                // This allows for testing without configuring IIS with a 
                // static IP or editing the local hosts file.
                httpContext.Request.QueryString["domain"]; 
#else
                null;
#endif
            if (string.IsNullOrEmpty(domain))
                domain = httpContext.Request.Headers["HOST"];

            return domains.Contains(domain);
        }
    }

Usage

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

        // This ignores Category/Cars for www.domain.com and www.foo.com
        routes.IgnoreRoute("Category/Cars", new { _ = new DomainConstraint("www.domain.com", "www.foo.com") });

        // Matches www.domain2.com/ and sends it to CategoryController.Cars
        routes.MapRoute(
            name: "HomePageDomain2",
            url: "",
            defaults: new { controller = "Category", action = "Cars" },
            constraints: new { _ = new DomainConstraint("www.domain2.com") }
        );

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

            // This constraint allows the route to work either 
            // on "www.domain.com" or "www.domain2.com" (excluding any other domain)
            constraints: new { _ = new DomainConstraint("www.domain.com", "www.domain2.com") }
        );
    }
}

If you fire this up in a new project in Visual Studio, you will notice it shows an error. This is because localhost:<port> is not a configured domain. However, if you navigate to:

/?domain=www.domain.com

You will see the home page.

This is because for the debug build only, it allows you to override the "local" domain name for testing purposes. You can configure your local IIS server to use a local static IP address (added to your network card) and add a local hosts file entry to test it locally without the query string parameter.

Note that when doing a "Release" build, there is no way to test using a query string parameter, as that would open up a potential security vulnerability.

If you use the URL:

/?domain=www.domain2.com

it will run the CategoryController.Cars action method (if one exists).

Note that since the Default route covers a wide range of URLs, most of the site will be available to both www.domain.com and www.domain2.com. For example, you will be able to reach the About page both at:

/Home/About?domain=www.domain.com
/Home/About?domain=www.domain2.com

You can use the IgnoreRoute extension method to block URLs that you don't want (and it accepts route constraints, so this solution will work there, too).

This solution will work if you largely want to share functionality between domains. If you would rather have 2 domains in one web site, but make them act like separate web sites, it would be easier to manage if you use an Area for each "web site" in your project by using the above route constraint for the Area routes.

public class Domain2AreaRegistration : AreaRegistration
{
    public override string AreaName
    {
        get
        {
            return "Domain2";
        }
    }

    public override void RegisterArea(AreaRegistrationContext context)
    {
        context.MapRoute(
            name: "Domain2_default",
            url: "{controller}/{action}/{id}",
            defaults: new { action = "Index", id = UrlParameter.Optional }, 
            constraints: new { _ = DomainConstraint("www.domain2.com") }
        );
    }
}

The above configuration would make every URL (that is 0, 1, 2, or 3 segments long) for www.domain2.com route to a controller in the Domain2 Area.