private tabComboBox as DataTable = new DataTable();

public void CARICA_COMBOBOX_DGW(DataGridView nome_dgw, string sql, string nometab, string campo_dispay, string campo_cod, int Width_campo, string intest)
{
SqlConnection conn = new SqlConnection(Properties.Settings.Default.CONNESSIONE_LOCALE);
SqlCommand cmd = new SqlCommand(sql, conn);

try
{
conn.Open();

SqlDataAdapter sqlda = new SqlDataAdapter(cmd);
sqlda.Fill(this.tabComboBox);

DataGridViewComboBoxColumn columnCb = new DataGridViewComboBoxColumn();
columnCb.DataPropertyName = "" + nometab + "";

columnCb.DataSource = this.tabComboBox;
columnCb.DisplayMember = "" + campo_dispay + "";
columnCb.ValueMember = "" + campo_cod + "";

columnCb.Width = Width_campo;
columnCb.HeaderText = "" + intest + "";

nome_dgw.Columns.Add(columnCb);

conn.Close();
}
catch (Exception ex)
{
MessageBox.Show(this, "ERRORE!\n" + ex.Message, "CARICA_COMBOBOX_DGW", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}