How can I change a route value then redirect to that route?

Question

I have a UserAccountController that takes routes like this "/{username}/{action}".

I'd like to create some functionality so that I can take a user to an account-specific page without knowing their username up front. I'd like to be able to use the URL "/your/{action}" which would catch the fact that "your" was sent as their username, get their real username (because they are logged in), and redirect them to "/their-actual-username/{action}".

I could do this in each of the controller actions, but I'd rather have it happen some place earlier that would do this for all of the controller actions. I attempted to do this in the Controller's Initialize method by changing the RouteData.Values["username"] to the real username then attempting to Response.RedirectToRoute(RouteData); Response.End() but that always took me to the wrong place (some completely wrong route).

---

Updated: Thanks to BuildStarted for leading me to this answer:

public class UserAccountController : Controller
{
    protected override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);

        if ((string) filterContext.RouteData.Values["username"] != "your") 
            return;

        var routeValues = new RouteValueDictionary(filterContext.RouteData.Values);
        routeValues["username"] = UserSession.Current.User.Username;
        filterContext.Result = new RedirectToRouteResult(routeValues);
    }
}

Answer 1

You can use the FilterAttribute with IActionFilter to accomplish what you want.

public class UserFilterAttribute : FilterAttribute, IActionFilter  {
    public void OnActionExecuted(ActionExecutedContext filterContext) {
    }

    public void OnActionExecuting(ActionExecutingContext filterContext) {
        var username = filterContext.RouteData.Values["username"];
        var realUserName = ""; //load from database
        filterContext.Result = new RedirectToRouteResult(new System.Web.Routing.RouteValueDictionary(new { controller = "Users", action = "Index", username = realUserName }));
    }
}

Then on your ActionResult in your controller you could apply [UserFilter] to the action.

[UserFilter]
public ActionResult UnknownUserHandler() {
    return View();
}

This should get you the results you're looking for. Any questions please post :)