private void capNhatSach_Load(object sender, EventArgs e)
        {
            dtpNgayNhap.Format       = DateTimePickerFormat.Custom;
            dtpNgayNhap.CustomFormat = "dd-MM-yyyy";

            connectSer.Connect();
            sachSer.getAll(dgvSach);
            connectSer.LoadDataCombobox(cbMaLinhVuc, "select MALV from tblLinhVuc");
            connectSer.LoadDataCombobox(cbTenLinhVuc, "select TENLV from tblLinhVuc");
        }