protected void Page_Load(object sender, EventArgs e) { string rawId = Request.QueryString["BookID"]; int bookId; if (!String.IsNullOrEmpty(rawId) && int.TryParse(rawId, out bookId)) { using (ShoppingCartActions usersShoppingCart = new ShoppingCartActions()) { usersShoppingCart.AddToCart(Convert.ToInt16(rawId)); } } else { Debug.Fail("ERROR : We should never get to AddToCart.aspx without a BookId."); throw new Exception("ERROR : It is illegal to load AddToCart.aspx without setting a BookId."); } Response.Redirect("ShoppingCart.aspx"); }