private void Form1_Load(object sender, EventArgs e)
        {
            ToolStripMenuItem item = new ToolStripMenuItem("最近打开文件1");
            item.Click += new EventHandler(item_Click);
            this.文件ToolStripMenuItem.DropDownItems.Add(item);
        }

        void item_Click(object sender, EventArgs e)
        {
            MessageBox.Show("这是最近打开文件的事件代码！");
        }