private void btnXoaMon_Click(object sender, EventArgs e)
        {
            DTO.Table table = lsvBill.Tag as DTO.Table;

            int idBill = BillDAO.Instance.GetUncheckBillIDByTableID(table.ID);
            int foodID = (cbFood.SelectedItem as Food).ID;
            int count  = (int)nmFoodCount.Value;


            BillInfoDAO.Instance.InsertBillInfo(idBill, foodID, -1);



            ShowBill(table.ID);
            LoadTable();
        }
        private void btnThanhtoan_Click(object sender, EventArgs e)
        {
            DTO.Table table = lsvBill.Tag as DTO.Table;

            int idBill   = BillDAO.Instance.GetUncheckBillIDByTableID(table.ID);
            int discount = (int)nmDiscount.Value;

            double totalPrice      = Convert.ToDouble(tbxTotalPrice.Text.Split(',')[0]) * 1000;
            double finaltotalprice = totalPrice - (totalPrice / 100) * discount;

            if (idBill != -1)
            {
                if (MessageBox.Show(string.Format("Bạn có chắc thanh toán hoá đơn cho bàn {0}\n Tổng tiền - (Tổng tiền / 100) x Giảm giá = {1} - ({1} / 100 x {2}) = {3}", table.Name, totalPrice, discount, finaltotalprice), "Thông báo", MessageBoxButtons.OKCancel) == System.Windows.Forms.DialogResult.OK)
                {
                    BillDAO.Instance.CheckOut(idBill, discount, (float)finaltotalprice);
                    ShowBill(table.ID);
                }
            }

            LoadTable();
        }