winform listbox 显示tooltip（防闪烁）

private void listBox1_MouseMove(object sender, MouseEventArgs e)
        {
            int index = listBox1.IndexFromPoint(e.Location);
            // Check if the index is valid.
            if (index != -1 && index < listBox1.Items.Count)
            {
                // Check if the ToolTip's text isn't already the one
                // we are now processing.
                if (toolTip1.GetToolTip(listBox1) != listBox1.Items[index].ToString())
                {
                    // If it isn't, then a new item needs to be
                    // displayed on the toolTip. Update it.
                    toolTip1.SetToolTip(listBox1, listBox1.Items[index].ToString());
                }
            }
        }