public long SavePhone(Phone phone)
        {
            var db = new SellPhoneDB();

            db.phones.Add(phone);
            return(db.SaveChanges());
        }
        public long SaveOrder(CustomerOrder order)
        {
            var db = new SellPhoneDB();

            db.CustomerOrders.Add(order);
            return(db.SaveChanges());
        }
        public long SaveOrderedPhone(OrdereredPhone orderPhone, long orderId)
        {
            var db = new SellPhoneDB();

            CustomerOrder order = db.CustomerOrders.Find(orderId);

            order.OrdereredPhones.Add(orderPhone);
            return(db.SaveChanges());
        }