private void btnThue_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < dgvThongtin.RowCount; i++)
            {
                if (Convert.ToBoolean(dgvThongtin.Rows[i].Cells["Thue"].Value) == true)
                {
                    if (dgvThongtin.Rows[i].Cells["TrangThai"].Value.ToString() == "Đã thuê")
                    {
                        MessageBox.Show("Phòng " + dgvThongtin.Rows[i].Cells["SoPhong"].Value.ToString() + " đã được thuê rồi. Chọn phòng khác!");
                        dgvThongtin.Rows[i].Cells["Thue"].Value = false;
                        return;
                    }
                    if (dgvThongtin.Rows[i].Cells["TrangThai"].Value.ToString() == "Hỏng")
                    {
                        MessageBox.Show("Phòng " + dgvThongtin.Rows[i].Cells["SoPhong"].Value.ToString() + " đang hỏng. Chọn phòng khác!");
                        dgvThongtin.Rows[i].Cells["Thue"].Value = false;
                        return;
                    }

                    ecPT.MaPh = dalPhong.getMaPh(dgvThongtin.Rows[i].Cells["SoPhong"].Value.ToString());
                    ecPT.MaKH = txtMaKH.Text;
                    DateTime date = DateTime.Now;
                    ecPT.MaPhieu = date.Day.ToString() + date.Month.ToString() + date.Hour.ToString() + date.Minute.ToString() + date.Second.ToString() + dgvThongtin.Rows[i].Cells["SoPhong"].Value.ToString();
                    ecPT.MaPT    = txtMaPT.Text;

                    dalPhieuthue.ThemThongTin(ecPT);

                    ecHD.MaHD        = ecPT.MaPhieu;
                    ecHD.MaPhieuThue = ecPT.MaPhieu;
                    ecHD.ThanhTien   = 0;
                    ecHD.Gia         = 200;
                    ecHD.NgayVao     = dtpNgayvao.Value.Year.ToString() + "-" + dtpNgayvao.Value.Month.ToString() + "-" + dtpNgayvao.Value.Day.ToString();
                    ecHD.NgayRa      = dtpNgayra.Value.Year.ToString() + "-" + dtpNgayra.Value.Month.ToString() + "-" + dtpNgayra.Value.Day.ToString();
                    dalHD.ThemThongTin(ecHD);

                    EC_Phong ecPh = new EC_Phong();
                    ecPh.MaPh      = dgvThongtin.Rows[i].Cells["MaPh"].Value.ToString();
                    ecPh.SoPhong   = dgvThongtin.Rows[i].Cells["SoPhong"].Value.ToString();
                    ecPh.TrangThai = "Đã thuê";
                    dalPh.SuaThongTin(ecPh);
                }
            }
            MessageBox.Show("Thuê OK!");

            DataTable tb = dalPh.ThongTinPhong("");

            dgvThongtin.DataSource = tb;
            for (int i = 0; i < dgvThongtin.RowCount; i++)
            {
                dgvThongtin.Rows[i].Cells["STT"].Value = i + 1;
                if (dgvThongtin.Rows[i].Cells["TrangThai"].Value.ToString() == "Tốt")
                {
                    dgvThongtin.Rows[i].DefaultCellStyle.BackColor = Color.Lime;
                }
                else
                if (dgvThongtin.Rows[i].Cells["TrangThai"].Value.ToString() == "Đã thuê")
                {
                    dgvThongtin.Rows[i].DefaultCellStyle.BackColor = Color.LightSkyBlue;
                }
                else
                if (dgvThongtin.Rows[i].Cells["TrangThai"].Value.ToString() == "Hỏng")
                {
                    dgvThongtin.Rows[i].DefaultCellStyle.BackColor = Color.Red;
                }
            }
        }