Global.asax.cs

//add using
using System.Web.Routing;


    public class Global : System.Web.HttpApplication
    {

        protected void Application_Start(object sender, EventArgs e)
        {
            RegisterRoutes(RouteTable.Routes);
        }
        
        
        public static void RegisterRoutes(RouteCollection routeCollection)
        {

            // product/product_id
            routeCollection.MapPageRoute("PRODUCT", "product/{id}", "~/product.aspx", false, null,
                new RouteValueDictionary { { "id", ".*?" } });
            // product/product_id/product_desc
            routeCollection.MapPageRoute("PRODUCT_DESC", "product/{id}/{desc}", "~/product.aspx", false, null,
                new RouteValueDictionary { { "id", ".*?" } });

         
        }

        
     }