ASP.Net MVC3: Set up Routing to handle multiple unique ID's?

Question

I'm building an MVC application that consists of entities that can be referenced by two different unique ID's, an ugly system generated ID, and a more user-friendly 5 character "Short Code". For example, I would like my end-users to be able to type the following url's in their browsers:

http://intranet/PRJ2011004

http://intranet/DEP42

Again, both codes are unique. I have the routing for the first URL correctly set up. When the user enters that URL, they receive the proper page displaying the index page for the entity: PRJ201104.

How do I set up the route to handle the second scenario? Preferably there is a way to "trick" MVC into changing the value it passes to the controller from the short code to the project.

I would like a way to intercept the 5 character short code route, take the value provided and look it up in my entities table, then if I find a matching record I would like to either (in order of preference):

1. Display the entities' index page while still retaining the short code in the url. In this scenario, I would like to "trick" the controller handling the route into thinking the "id" passed in is actually the unique ID and not the short code (in order to not have to refactor my existing code)
2. Re-direct the url to the one with the working unique (ugly) ID.

And if I don't find a matching Entity using that short code value I would let my standard route handling continue (so, for example, my "Error" and "Admin" controllers, which are both 5 characters as well but not Short Codes, will continue to work appropriately).

TIA

Answer 1

A custom route could do the job:

public class MyRoute : Route
{
    public MyRoute(string url, object defaults)
        : base(url, new RouteValueDictionary(defaults), new MvcRouteHandler())
    { }

    public override RouteData GetRouteData(HttpContextBase httpContext)
    {
        var rd = base.GetRouteData(httpContext);
        var id = rd.Values["id"] as string;
        if (id == null)
        {
            return rd;
        }

        // TODO: if you think that the id provided is a pretty id
        // query the database to fetch the other id

        if (IsPrettyId(id))
        {
            id = FetchCorrespondingId(id);
            rd.Values["id"] = id;
        }
        return rd;
    }
}

and then register this custom route:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.Add(
        "Default",
        new MyRoute(
            "{controller}/{action}/{id}",
            new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        )
    );
}

Now inside the controller action you will always have the long ugly id:

public ActionResult Index(string id)
{

}