private void txtGiaTriTimKiem_KeyUp(object sender, KeyEventArgs e)
        {
            string colName   = cmCotTimKiem.Text;
            string strFilter = txtGiaTriTimKiem.Text.Trim();

            dgvDanhMucNhanVien.DataSource = dbNhanVien.Fillter(colName, strFilter);
            foreach (DataGridViewRow row in dgvDanhMucNhanVien.Rows)
            {
                row.HeaderCell.Value = (row.Index + 1).ToString();
            }
            dgvDanhMucNhanVien.AutoResizeRowHeadersWidth(DataGridViewRowHeadersWidthSizeMode.AutoSizeToAllHeaders);
        }