ASP.NET Routing : RouteCollection class missing

I am developing a website(web forms , not MVC) in VS 2008(with SP1 ).I am trying to incorporate the ASP.NET Routing.I am following the MSDN tutorial to do it. http://msdn.microsoft.com/en-us/library/cc668201.aspx I have added the below items to my glbal.asax.cs file as per the tutorial ``` protected void Application_Start(object sender, EventArgs e) { RegisterRoutes(RouteTable.Routes); } public static void RegisterRoutes(RouteCollection routes) { routes.Add(new Route ( "Category/{action}/{categoryName}" , new CategoryRouteHandler() )); } ``` When trying to build it is telling like "The type or namespace name 'RouteCollection' could not be found (are you missing a using directive or an assembly reference?) I have System.web imported to my global.asax file Any Idea how to get rid of it ?