Url.RouteUrl returns null

[pcreativedvx]

I'm buiding a UrlHelper for a route as in best practicesthe problem is that the returned value is always null when debugging in found that Url.RouteUrl("x") return nullUrl.RouteCollection["X"] return Routei'm trying to do :\[code\]public static string Category(this UrlHelper helper, int Id, string category){ return helper.RouteUrl("X", new {id = Id, category= category});}\[/code\]I can't see where I'm doing something wrong