ToolStrip失去焦点时，点击第二次才执行事件的解决方法

class ToolStripEx : ToolStrip
{
    protected override void WndProc(ref Message m)
    {
        const int WM_MOUSEACTIVATE = 0x21;
        if (m.Msg == WM_MOUSEACTIVATE && this.CanFocus && !this.Focused)
            this.Focus();
        base.WndProc(ref m);
    }
}