问DatagridView CheckBox检查返回FormatExceptiion

EN

private void populatedataGrid()
{
  String sql = "SELECT pm.Name, pm.telephone, pm.email, pm.validID, comp.name as `Company` FROM `project managers`as pm JOIN `companies`as comp ON pm.Companies_companyID = comp.companyID where pm.Companies_companyID =" + loginID;
  MySqlCommand command = new MySqlCommand(sql, dh.Connection);
            
  try
  {
    MySqlDataAdapter adapter = new MySqlDataAdapter();
    adapter.SelectCommand = command;
    DataTable dbdataset = new DataTable();
    adapter.Fill(dbdataset);
    BindingSource bSource = new BindingSource();
                
    // DataGridView1 is a different DataGrid, i am working on DataGridView2
    bSource.DataSource = dbdataset;
    dataGridView1.DataSource = bSource;
    dataGridView2.DataSource = bSource;
    //Method for adding the additional column with checkboxes (ill paste the method below)
    addCheckBoxColumn();
    //I make it so that only the checkboxes can be edited
    foreach (DataGridViewColumn dc in dataGridView2.Columns)
    {
      if (dc.Index.Equals(5))
      {
        dc.ReadOnly = false;
      }
      else
      {
        dc.ReadOnly = true;
      }
    }
    adapter.Update(dbdataset);
  }
  catch (Exception ex)
  {
    MessageBox.Show(ex.Message);
  }
  finally
  {
    dh.Connection.Close();
  }
}

private void addCheckBoxColumn()
{
  DataGridViewCheckBoxColumn cbCol = new DataGridViewCheckBoxColumn();
  cbCol.ValueType = typeof(bool);
  cbCol.Name = "Select";
  cbCol.HeaderText = "Select";
  dataGridView2.Columns.Add(cbCol);
}

private void button1_Click(object sender, EventArgs e)
{
  int counter = 0;
  foreach (DataGridViewRow row in dataGridView2.Rows)
  {
    if (Convert.ToBoolean(row.Cells[5].Value))
    {
      counter++;
    }
  }
  label2.Text = counter.ToString();
}