private void btnTim_Click(object sender, EventArgs e)
 {
     frmTimKiemNCC frmTK = new frmTimKiemNCC();
     frmTK.ShowDialog();
     str = frmTK.maNCC;
     DataTable tblNhaCC = new DataTable();
     tblNhaCC = BLL.show1NCC(str);
     dgvNhaCC.DataSource = tblNhaCC;
 }