问如何防止ContextMenu被限制在其容器中(Win Forms c#)

EN

/// <summary>
/// TextBox which can auto complete words found in a table column
/// Just set DataSource and DataListField and start typing - WD
/// </summary>
public class AutoComplete : TextBox
{
    public DataTable DataSource { get; set; }
    public string DataListField { get; set; }
    private ContextMenuStrip SuggestionList = new ContextMenuStrip();

    public AutoComplete()
    {
        this.LostFocus += new EventHandler(AutoComplete_LostFocus);
        KeyUp += new KeyEventHandler(AutoComplete_KeyUp);
        SuggestionList.ItemClicked += new ToolStripItemClickedEventHandler(SuggestionList_ItemClicked);
    }

    void AutoComplete_LostFocus(object sender, EventArgs e)
    {
        if (!SuggestionList.Focused)
        {
            SuggestionList.Visible = false;
        }
    }

    void SuggestionList_ItemClicked(object sender, ToolStripItemClickedEventArgs e)
    {
        this.Text = e.ClickedItem.Text;
        SuggestionList.Visible = false; 
        this.Focus();
        SuggestionList.Visible = false;
    }

    void AutoComplete_KeyUp(object sender, KeyEventArgs e)
    {
        if (null != DataSource && DataSource.Rows.Count > 0 && null != DataListField)
        {
            if (e.KeyCode != Keys.Enter)
            {
                if (SuggestionList.Items.Count > 0 && e.KeyCode == Keys.Down)
                {
                    SuggestionList.Focus();
                    SuggestionList.Items[0].Select();
                    SuggestionList.BringToFront();
                }
                else if (this.Text.Length > 0)
                {
                    SuggestionList.Items.Clear();

                    DataRow[] drSuggestionList = DataSource.Select("[" + DataListField + "] LIKE '" + this.Text + "%'");

                    foreach (DataRow dr in drSuggestionList)
                    {
                        SuggestionList.Items.Add(dr[DataListField].ToString());
                    }

                    SuggestionList.TopLevel = false;
                    SuggestionList.Visible = true;
                    SuggestionList.Top = (this.Top + this.Height);
                    SuggestionList.Left = this.Left;
                    this.Parent.Controls.Add(SuggestionList);
                    SuggestionList.BringToFront();
                }
            }
        }
    }

}