private void btnThemMoi_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e)
        {
            frmThemMoiHocSinh frm = new frmThemMoiHocSinh();

            frm.ShowDialog();
            HienThiThongTinHS();
        }
        private void btnCapNhatTT_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e)
        {
            string MaHS = "";

            MaHS = "" + gridThongTin.CurrentRow.Cells[3].Value;
            frmThemMoiHocSinh frm = new frmThemMoiHocSinh();

            frm.MaHS = MaHS;
            frm.ShowDialog();
        }