我也得到了同样的问题。我有一个替代的解决方案如下所述：

I've also got the same problem. I got an alternative solution as described below:

1. 插入一个定时器控制
2. 我在一个面板容器中添加的控件

3. 和做了以下

1. Insert a timer control
2. I've added the controls in a panel container

3. And did the following

private void timer1_Tick(object sender, EventArgs e)
{
    if ((int)MdiChildren.GetLength(0) > 0)
    {
        panel1.Visible = false;
    }
    else
    {
        panel1.Visible = true;
    }
}