product.aspx.cs

       
       
       protected void Page_Load(object sender, EventArgs e)
       {

            var product_id = "";

            product_id = Request["id"];

            if (string.IsNullOrEmpty(id))
            {
                if (Page.RouteData.Values["id"] != null)
                    id = Page.RouteData.Values["id"].ToString();

            }


            if (string.IsNullOrEmpty(id))
            {
                Response.Redirect("/ProductList");
                return;
            }
            
            
            //...