stackoverflow URL rewrite

Question

How does SO perform the URL rewrite if we only put in the question ID?

questions/{id}/{whatever}

to

questions/{id}/{question-slug}

I've been working for some time with MVC and I have it working (routes, action, everything) so that it picks up the right content based on the provided ID.

However, the part after the {id} (the slug part) stays the same as typed in. So if someone typed in content/5/foobar it will display the right content but will leave the foobar in there.

In the controller (or somewhere else, please suggest where) I would need to go into the DB and pull out the right slug, put it in the route data and then perform a redirect to the same action with this correct data, I guess?

This is a try with Execute Result override. It works but does not redirect or replace/display the correct URL in browser:

    protected override void Execute(System.Web.Routing.RequestContext requestContext) {

        if (requestContext.RouteData.Values["id"] != null) {
            string currentSlug = _repository.Find(int.Parse(requestContext.RouteData.Values["id"].ToString())).Slug;
            if (requestContext.RouteData.Values["slug"] != null) {
                requestContext.RouteData.Values.Remove("slug");
            }
            requestContext.RouteData.Values.Add("slug", currentSlug);
        }

        base.Execute(requestContext);
    }

This is another, nicely working, version of a Display action, so you can see what it does and get an idea what I want:

    //
    // GET: {culture}/directory/5/{slug}
    public virtual ActionResult Display(int id, string slug)
    {
        var model = _repository.Find(id);
        if (model != null) {
            if (!model.Slug.Equals(slug, System.StringComparison.OrdinalIgnoreCase)) {
                return RedirectToActionPermanent(pndng.DirectoryEntry.ActionNames.Display, pndng.DirectoryEntry.Name, new { id = model.Id, slug = model.Slug });
            }
            return View(model);
        }
        // no model found
        return InvokeHttp404(HttpContext);
    }

This one performs permanent redirect (it does what I want) but is it right? I guess I need a redirect to refresh the browser URL, don't I?

Answer 1

  public ActionResult Details(int id, string slug)
        {
            var session = MvcApplication.CurrentRavenSession;

            var blogPostRelations = session
                .Query<BlogPost, BlogPosts_WithRelatedData>()
                .Where(x => x.IntId == id)
                .As<BlogPostRelations>()
                .FirstOrDefault()
                ;


            if (blogPostRelations == null)
                return HttpNotFound();

            if (blogPostRelations.BlogPost.DisplayData.Slug.Value != slug)
                return RedirectToActionPermanent("Details", new { id = id, slug = blogPostRelations.BlogPost.DisplayData.Slug.Value });

            return View(blogPostRelations);
        }

Notice the:

if (blogPostRelations.BlogPost.DisplayData.Slug.Value != slug)
                    return RedirectToActionPermanent("Details", new { id = id, slug = blogPostRelations.BlogPost.DisplayData.Slug.Value });

So your #2 approach is the right one.

Answer 2

You could write a custom route for this:

public class QuestionsRoute : Route
{
    public QuestionsRoute()
        : base(
            "questions/{id}/{slug}",
            new RouteValueDictionary(new
            {
                controller = "questions",
                action = "index",
                slug = UrlParameter.Optional
            }),
            new RouteValueDictionary(new
            {
                id = @"\d+"
            }),
            new MvcRouteHandler()
        )
    { }

    public override RouteData GetRouteData(HttpContextBase httpContext)
    {
        var rd = base.GetRouteData(httpContext);
        if (rd == null)
        {
            return null;
        }

        var id = rd.GetRequiredString("id");
        var slug = rd.Values["slug"] as string;
        if (string.IsNullOrEmpty(slug))
        {
            slug = GoFetchSlugFromDb(id);
            if (string.IsNullOrEmpty(slug))
            {
                return null;
            }

            httpContext.Response.RedirectToRoutePermanent(new
            {
                action = "index",
                controller = "questions",
                id = id,
                slug = slug
            });
            return null;
        }
        return rd;
    }

    private string GoFetchSlugFromDb(string id)
    {
        // TODO: you know what to do here
        throw new NotImplementedException();
    }
}

which will be registered in Application_Start:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.Add("questions", new QuestionsRoute());
}

Now your QuestionsController will be pretty simple:

public class QuestionsController: Controller
{
    public ActionResult Index(int id, string slug)
    {
        ...
    }
}