Preserve Case in Route Parameters with LowercaseUrls enabled

Question

I am using routes.LowercaseUrls = true; in my MVC 4 application which is working great. However, parameters will also get lowercased, so if I have a route like

routes.MapRoute(
    name: "MyController",
    url: "foo/{hash}/{action}",
    defaults: new { controller = "MyController", action = "Details" }
);

The link generated with

@Html.ActionLink("my link", "Details", new { hash=ViewBag.MyHash })

will have the {hash}-part of the URL lowercased as well, for example if ViewBag.MyHash = "aX3F5U" then the generated link will be /foo/ax3f5u instead of /foo/aX3F5U

Is there a way to force MVC to only lowercase the controller and action parts?

For older versions of MVC, the way to go seemed to be to implement a custom subclass of Route, however I don't know how/where to instantiate it, since the signature of the route constructors is quite different to MapRoute and I'm hoping there to be a simpler way.

Answer 1

I think the solution with a custom subclass of Route will be a good enough and simple, but at the same time a little bit ugly :)

You can add a CustomRoute at RegisterRoute method of RouteConfig.cs. Add the following code instead of routes.MapRoute

var route = new CustomRoute(new Route(
  url: "{controller}/{action}/{id}",
  defaults: new RouteValueDictionary() { 
    { "controller", "Home" }, 
    { "action", "Index" }, 
    { "id", UrlParameter.Optional }
  },
  routeHandler: new MvcRouteHandler()
));
routes.Add(route);

Implementaion of particular CustomRoute may look like this:

public class CustomRoute : RouteBase
{
  private readonly RouteBase route;

  public CustomRoute(RouteBase route)
  {
    this.route = route;
  }

  public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
  {
    values = new RouteValueDictionary(values.Select(v =>
    {
      return v.Key.Equals("action") || v.Key.Equals("controller")
        ? new KeyValuePair<String, Object>(v.Key, (v.Value as String).ToLower())
        : v;
    }).ToDictionary(v => v.Key, v => v.Value));

    return route.GetVirtualPath(requestContext, values);
  }

  public override RouteData GetRouteData(HttpContextBase httpContext)
  {
    return route.GetRouteData(httpContext);
  }
}

However it's not an optimal implementation. A complete example could use a combination of extensions on RouteCollection and a custom Route child to keep it as close as possible to the original routes.MapRoute(...) syntax:

LowercaseRoute Class:

public class LowercaseRoute : Route
{
    public LowercaseRoute(string url, IRouteHandler routeHandler) : base(url, routeHandler) { }

    public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
    {
        values = new RouteValueDictionary(values.Select(v =>
        {
            return v.Key.Equals("action") || v.Key.Equals("controller")
              ? new KeyValuePair<String, Object>(v.Key, (v.Value as String).ToLower())
              : v;
        }).ToDictionary(v => v.Key, v => v.Value));

        return base.GetVirtualPath(requestContext, values);
    }
}

RouteCollectionExtensions Class:

public static class RouteCollectionExtensions
{
    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url)
    {
        return MapLowercaseRoute(routes, name, url, null /* defaults */, (object)null /* constraints */);
    }

    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url, object defaults)
    {
        return MapLowercaseRoute(routes, name, url, defaults, (object)null /* constraints */);
    }

    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url, object defaults, object constraints)
    {
        return MapLowercaseRoute(routes, name, url, defaults, constraints, null /* namespaces */);
    }

    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url, string[] namespaces)
    {
        return MapLowercaseRoute(routes, name, url, null /* defaults */, null /* constraints */, namespaces);
    }

    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url, object defaults, string[] namespaces)
    {
        return MapLowercaseRoute(routes, name, url, defaults, null /* constraints */, namespaces);
    }

    [SuppressMessage("Microsoft.Design", "CA1054:UriParametersShouldNotBeStrings", MessageId = "2#", Justification = "This is not a regular URL as it may contain special routing characters.")]
    public static Route MapLowercaseRoute(this RouteCollection routes, string name, string url, object defaults, object constraints, string[] namespaces)
    {
        if (routes == null)
        {
            throw new ArgumentNullException("routes");
        }
        if (url == null)
        {
            throw new ArgumentNullException("url");
        }

        Route route = new LowercaseRoute(url, new MvcRouteHandler())
        {
            Defaults = CreateRouteValueDictionary(defaults),
            Constraints = CreateRouteValueDictionary(constraints),
            DataTokens = new RouteValueDictionary()
        };

        if ((namespaces != null) && (namespaces.Length > 0))
        {
            route.DataTokens["Namespaces"] = namespaces;
        }

        routes.Add(name, route);

        return route;
    }

    private static RouteValueDictionary CreateRouteValueDictionary(object values)
    {
        var dictionary = values as IDictionary<string, object>;
        if (dictionary != null)
        {
            return new RouteValueDictionary(dictionary);
        }

        return new RouteValueDictionary(values);
    }
}

You can now use MapLowercaseRoute instead of MapRoute, so

routes.MapRoute(
    name: "MyController",
    url: "foo/{hash}/{action}",
    defaults: new { controller = "MyController", action = "Details" }
);

simply becomes

routes.MapLowercaseRoute(
    name: "MyController",
    url: "foo/{hash}/{action}",
    defaults: new { controller = "MyController", action = "Details" }
);

exposing the desired behaviour.

Answer 2

Here is one simple way to do this,

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

    public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
    {
        if (values["action"] != null)
            values["action"] = values["action"].ToString().ToLowerInvariant();
        if (values["controller"] != null)
            values["controller"] = values["controller"].ToString().ToLowerInvariant();
        return base.GetVirtualPath(requestContext, values);
    }
}

routes.Add("Default",new MyRoute("{controller}/{action}/{id}",
                new { controller = "Home", action = "Index", id = MyUrlParameter.Optional }));

See this blog post for detail.