Why the query strings in my ASP.NET MVC route?

Question

On an ASP.NET MVC (Beta) site that I am developing sometimes calls to ActionLink will return to me URLs containing querying strings. I have isolated the circumstances that produce this behavior, but I still do not understand why, instead of producing a clean URL, it decides to using a query string parameter. I know that functionally they are the same, but for consistency (and appearance) of the URLs this is not what I want.

Here are my routes:

routes.MapRoute(
    "Photo Gallery Shortcut",
    "group/{groupname}",
    new { controller = "Photos", action = "All", Id = "" });

routes.MapRoute(
    "Tagged Photos", //since the Tagged action takes an extra parameter, put it first
    "group/{groupname}/Photos/Tagged/{tagname}/{sortby}",
    new { controller = "Photos", action = "Tagged", Id = "", SortBy = "" });

routes.MapRoute(
    "Photo Gallery", //since the Gallery's defualt action is "All" not "Index" its listed seperatly
    "group/{groupname}/Photos/{action}/{sortby}",
    new { controller = "Photos", action = "All", Id = "", SortBy = "" });

routes.MapRoute(
    "Group",  //<-- "Group" Category defined above
    "group/{groupname}/{controller}/{action}/{id}",
    new {controller = "Photos", action = "Index", Id = ""});

Now the problem only occurs when I am looking at the view described by the route named "Tagged Photos" and execute ActionLink via:

Html.ActionLink<PhotosController>(p => p.All((string)ViewData["group"], ""), "Home")

Which produces the URL:

http://domain/group/GROUPNAME?sortBy=

From any other view the URL produced is:

http://domain/group/GROUPNAME

I have pulled down Phil's ASP.NET Routing Debugger, and everything appears in order. This one has me stumped. Any ideas?

Answer 1

Not sure why different views are producing different URLs.

But you can get rid of that sortBy param by assigning a default value to the first route.

new { sortBy = "" }

During generation, if sortBy matches the default, the route engine will skip that parameter (if it's in the query string).