How to fill DataGridview comboBox cell with Db value

if (dtbl.Rows.Count > 0)

foreach (DataRow row in dtbl.Rows)

{

DataGridViewComboBoxCell cbCell = (DataGridViewComboBoxCell)dgvLicenseMembers.Rows[0].Cells["dgvCmbNationality"];

cbCell.DataSource = dtbl;

cbCell.DisplayMember = "CountryName";

cbCell.ValueMember = "CountryID";

cbCell.Items.Add(row["CountryName"].ToString()); // ! Getting ERROR -Items collection cannot be modified when the DataSource property is set.

}

sqlCon.Close();

}