public void AddToCart(int id, string returnUrl)
        {
            Product product = repository.Products
                              .FirstOrDefault(p => p.Id == id);
            CartForInvoice tt = null;

            if (product != null)
            {
                tt = GetCart();
                tt.AddItem(product, 1);
            }
            //var s = returnUrl.Split('/');
            string seriz = JsonConvert.SerializeObject(tt);

            httpContext.Response.Cookies.Delete(session);
            httpContext.Response.Cookies.Append(session, seriz);
            tt = GetCart();
        }