how to populate combobox with datagridview value

private void dgridregistration_CellClick(object sender, DataGridViewCellEventArgs e)
    {

    if (e.RowIndex >= 0)
        {
        DataGridViewRow row = this.dgridregistration.Rows[e.RowIndex];
        txtmemfname.Text = row.Cells["fname"].Value.ToString();
        txtmemmname.Text = row.Cells["mname"].Value.ToString();
        txtmemlname.Text = row.Cells["lname"].Value.ToString();
        rchtxtmemaddress.Text = row.Cells["address"].Value.ToString();
        cmbmemstate1.Text = row.Cells["state_name"].Value.ToString();
        cmbmemcity1.Text = row.Cells["city_name"].Value.ToString();
        txtbdate.Text = row.Cells["bdate"].Value.ToString();
        txtmempincode.Text = row.Cells["pincode"].Value.ToString();
        cmbmemoccupation1.Text = row.Cells["occupation"].Value.ToString();
        cmbmembgroup1.Text = row.Cells["blood_id"].Value.ToString();
        }
    }