C#

#region Configure MenuItem

private bool MyFormStarted = false;
private MyForm MyDlg;

private void MyDlgMenuItem_Click(object sender, EventArgs e)
{
    if (MyFormStarted)
    {
        if (MyDlg.InvokeRequired)
        {
            MyDlg.BeginInvoke((ThreadStart)delegate()
            {
                //MyDlg.Show();
                //MyDlg.BringToFront();
                //MyDlg.Focus();
            });
        }
        else
        {
            //MyDlg.Show();
            //MyDlg.BringToFront(); 
            //MyDlg.Focus();
        }
    }
    else
    {
        MyFormStarted = true;

        new Thread(new ThreadStart(delegate
        {
            MyDlg = new MyForm ();
            MyDlg.ShowDialog();
            MyDlg.Dispose();

            MyFormStarted = false;
        })).Start();
    }
}

#endregion

MyDlg.BringToFront(); 
MyDlg.Focus();

<br />
DataGridViewComboBoxColumn column = new DataGridViewComboBoxColumn();<br />
column.HeaderText = "SELECT";<br />
column.Name = "ItemSelect";<br />
column.CellTemplate = new DataGridViewComboBoxCell();<br />
column.Items.AddRange("One", "Two", "Three");<br />
column.DropDownWidth = 160;<br />
column.Width = 90;<br />
column.MaxDropDownItems = 3;<br />
column.FlatStyle = FlatStyle.Flat;<br />
myDataViewGrid.Columns.Insert(0, column);<br />