Routing to controller with a required, non-empty Guid parameter - asp.net-mvc

Question

I would like to map http://localhost/Guid-goes-here to ResellerController and fire Index action of that controller only when Guid-goes-here is not the empty Guid.
My routing table looks like this:
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Reseller",
"{id}",
new { controller = "Reseller", action = "Index", id = Guid.Empty }
// We can mark parameters as UrlParameter.Optional, but how to make it required?
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}
The action on the ResellerController looks like this:
public ActionResult Index(Guid id)
{
// do some stuff with non-empty guid here
}
Once the application has started, navigating to http://localhost routes me to the ResellerController with the empty Guid as the argument to the Index action's id parameter.

Answer 1

public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Reseller",
"{id}",
new { controller = "Reseller", action = "Index", id = UrlParameter.Optional },
new { id = #"^(\{{0,1}([0-9a-fA-F]){8}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){12}\}{0,1})$" }
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}
or if you want a more robust constraint than some cryptic regex:
public class GuidConstraint : IRouteConstraint
{
public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
{
var value = values[parameterName] as string;
Guid guid;
if (!string.IsNullOrEmpty(value) && Guid.TryParse(value, out guid))
{
return true;
}
return false;
}
}
and then:
routes.MapRoute(
"Reseller",
"{id}",
new { controller = "Reseller", action = "Index", id = UrlParameter.Optional },
new { id = new GuidConstraint() }
);

Answer 2

You need to include a constraint in the routing definition. Have a look on this post: http://blogs.microsoft.co.il/blogs/bursteg/archive/2009/01/11/asp-net-mvc-route-constraints.aspx