C#如何检测Excel是否失去焦点

我有一个Excel加载项（用C#和ExcelDNA编写），它的表单允许用户将数据输入从文本框继承的控件中。形式是模态的。进入控件会导致出现一个上下文菜单，其中包含基于用户输入的选项

如果用户已输入数据且contextmenu可见，然后用户使另一个应用程序成为活动应用程序，则contextmenu将覆盖该应用程序

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是否存在一个事件，我可以使用Excel应用程序的关闭来确定Excel已失去焦点？

我找到了一种方法，使contextmenu显示，而不包括其他项目。我的问题是，在输入textbox期间，contextmenu始终可见，因为我在textbox TextChanged事件中将AutoClose属性设置为false。现在，我在重新填充项目列表时，在TextChanged事件中将AutoClose属性设置为false。在输入第三个字符后，对输入文本框的任何击键都会执行此操作

然后，我创建了一个contextmenu关闭事件，如下所示：

    #region Instance Variables
    ContextMenuStrip menuStrip = new System.Windows.Forms.ContextMenuStrip();
    public event EventHandler EntryComplete;
    public event EventHandler EntryNotComplete;
    public event EventHandler EntryError;
    #endregion

    // Control Constructor
    public AutoCompleteTextBox()
    {
        InitializeComponent();

        menuStrip.PreviewKeyDown += menuStrip_PreviewKeyDown;
        this.Leave += AutoCompleteTextBox_Leave;

        // Use closing event so that we can determine when to close the menustrip.
        menuStrip.Closing += new ToolStripDropDownClosingEventHandler(menuStrip_Closing);
    }

    void menuStrip_Closing(object sender, ToolStripDropDownClosingEventArgs e)
    {
        // only close the menu strip when an item is selected or the application loses focus
        if (e.CloseReason != ToolStripDropDownCloseReason.ItemClicked &&
            e.CloseReason != ToolStripDropDownCloseReason.AppFocusChange)
        {
            e.Cancel = true;
        }
    }

    private void AutoCompleteTextBox_TextChanged(object sender, EventArgs e)
    {
        .
        .
        .
        try
        {
            // get information on whether a ToolbarMenuItem has been selected
            MenuItem info = new MenuItem();
            MenuItemInfo selectedToolStripMenuInfo = info.SelectedItem(menuStrip);

            menuStrip.AutoClose = true;
            menuStrip.Visible = false;
            menuStrip.Items.Clear();

            if (selectedToolStripMenuInfo == null)
            {
                EntryNotComplete(sender, e);
            }

            if (base.Text.Length >= 3 && selectedToolStripMenuInfo == null)
            {
                .
                .
                .

                menuStrip.AutoClose = false;

                // foreach loop to add items into list
                foreach (SearchType item in lst)
                {
                    szMenuItem = ...;

                    ToolStripItem tsItem = new ToolStripMenuItem();
                    tsItem.Text = szMenuItem;
                    tsItem.Name = item.DealId;
                    tsItem.Click += tsItem_Click;
                    tsItem.Font = new Font("Courier New", 8.0F, FontStyle.Italic);
                    menuStrip.Items.Add(tsItem);
                }

                Point point = base.Location;
                point.Offset(2, base.Height + 2);
                point = base.GetPositionFromCharIndex(base.SelectionStart);
                point.Offset(2, base.Font.Height + 2);

                base.ContextMenuStrip = menuStrip;
                base.ContextMenuStrip.Show(base.PointToScreen(point));
                base.Focus();

                menuStrip.AutoClose = true;
            }
            else if (base.Text.Length >= 3 && selectedToolStripMenuInfo != null)
            {
                EntryComplete(sender, e);
            }
        }
        catch (Exception ex)
        {
            ErrorDescription = ex.Message;
            menuStrip.AutoClose = true;
            menuStrip.Visible = false;
            EntryError(sender, e);
        }
    }