private void btnTimKiem_Click(object sender, EventArgs e)
        {
            DataTable dtTimKiemKhachHang = new DataTable();

            if (cboTimKiem.EditValue as string == "Mã khách hàng")
            {
                string timkiem = string.Format("MAKH LIKE N'%{0}%'", txtTimKiem.EditValue);
                dtTimKiemKhachHang            = khControl.getAllDataSeach(timkiem);
                gcTimKiemKhachHang.DataSource = dtTimKiemKhachHang;
            }
            else if (cboTimKiem.EditValue as string == "Tên khách hàng")
            {
                string timkiem = string.Format("TENKH LIKE N'%{0}%'", txtTimKiem.EditValue);
                dtTimKiemKhachHang            = khControl.getAllDataSeach(timkiem);
                gcTimKiemKhachHang.DataSource = dtTimKiemKhachHang;
            }
        }