ASP.NET MVC Problem with Re-use query parameters

Question

I have this routes:

routes.MapRoute(
                "Default",
                "user/{userId}/{controller}/{action}",
                new {controller = "Home", action = "Index" }
                );

            routes.MapRoute(
                "Short",
                "{controller}/{action}",
                new { controller = "Home", action = "Index"}
                );

My current location in browser:

http://my_site/user/197/UserEvents

On this page there are links:

@Html.ActionLink("Friends", "Index", "Friends")
@Html.ActionLink("Information", "Index", "UserInfo", new { userId = (string)null },null)

MVC re-use query parameters , so the first generated link:

my_site/user/197/Friends

The second link is generated:

my_site/UserInfo?userId=197

Why userId in the second link has a value of 197? Why not have a link:

my_site/UserInfo

Answer 1

I cannot pinpoint the exact location where MVC decides to reuse whatever route values it has at hand, but here's what I use in my projects:

//
// This fixes "ambient values" problem:
// http://stackoverflow.com/questions/2651675/asp-net-mvc-html-actionlink-maintains-route-values
// http://stackoverflow.com/questions/780643/asp-net-mvc-html-actionlink-keeping-route-value-i-dont-want
return new UrlHelper(
    new RequestContext(
        HttpContext.Current, 
        new RouteData {
            Route = urlHelper.RequestContext.RouteData.Route,
            RouteHandler = urlHelper.RequestContext.RouteData.RouteHandler
        }), urlHelper.RouteCollection)
    .Action(actionName, controllerName, routeValuesWithArea);

The key here is that neither RouteData.DataTokens nor RouteData.Values aren't set, so there's nothing MVC can possibly reuse.

Answer 2

I would probably do something like

http://foo.com/user/events/197

http://foo.com/user/events?userId=197

I find that the more I try to jive with ASP.NET routing conventions the more time I can send developing my app.

public class UserController : Controller
{
    public ActionResult Events(long userId)
    {
        //Do Something...
    }
}

public class FriendsController : Controller
{
    public ActionResult Index(long userId)
    {
        //Do Something...
    }
}