private void btnThemMoi_Click(object sender, EventArgs e)
        {
            frmThemQuanLiGiangDay frmThem = new frmThemQuanLiGiangDay();

            frmThem.ShowDialog();
            GetThongTinGiangDay();
        }
        private void btnChinhSua_Click(object sender, EventArgs e)
        {
            DataGridViewRow dgr = dgvQuanLiGiangDay.CurrentRow;

            if (dgvQuanLiGiangDay.SelectedRows.Count <= 0)
            {
                MessageBox.Show("Chọn bản ghi cần sửa!");
            }
            else
            {
                QuanLiGiangDay ql = new QuanLiGiangDay();
                ql.MaGiaoVien  = dgr.Cells["magiaovien"].Value.ToString();
                ql.MaMonHoc    = dgr.Cells["mamonhoc"].Value.ToString();
                ql.MaLop       = dgr.Cells["tenlop"].Value.ToString();
                ql.TietHoc     = dgr.Cells["tiethoc"].Value.ToString();
                ql.DiaDiem     = dgr.Cells["diadiem"].Value.ToString();
                ql.NgayBatDau  = DateTime.Parse(dgr.Cells["ngaybatdau"].Value.ToString());
                ql.NgayKetThuc = DateTime.Parse(dgr.Cells["ngayketthuc"].Value.ToString());
                frmThemQuanLiGiangDay frmThem = new frmThemQuanLiGiangDay(ql, true);
                frmThem.ShowDialog();
                GetThongTinGiangDay();
            }
        }