private void btnThanhtoan_Click(object sender, EventArgs e)
{
int sum = 0;
for (int i = 0; i < dgvThongtin.Rows.Count; i++)
{
sum += int.Parse(dgvThongtin.Rows[i].Cells["Gia"].Value.ToString());
}
_Gia = int.Parse(cn.GetValue(@"select DonGiaHT from tblHoaDon where MaHD = '" + cmbMahd.Text + "'"));
sum += getCost(dtpNgayVao.Value, dtpNgayra.Value, _Gia);
MessageBox.Show("Tổng số tiền thanh toán: " + sum.ToString());
//update hoa don
ecHD.ThanhTien = sum.ToString();
ecHD.MaHD = cmbMahd.Text;
dalHD.ThanhToan(ecHD);
//thay doi thong tin phong
EC_Phong ph = new EC_Phong();
ph.MaPh = cn.GetValue(@"select MaPh from tblPhieuThue where MaPhieu = '" + cmbMahd.Text + "'");
ph.TrangThai = "Tốt";
dalPh.TraPhong(ph);
cmbKhachhang.ResetText();
cmbMahd.ResetText();
dgvThongtin.DataSource = null;
}