public string CartAmountTotal(int?CustomerId)
        {
            List <CartAmountTotal_Result> obj = new List <CartAmountTotal_Result>();

            using (var entities = new SedapExpressEntities())
            {
                obj = entities.CartAmountTotal(CustomerId).ToList <CartAmountTotal_Result>();
            }

            return(JsonConvert.SerializeObject(obj));
        }