C#中怎样在ToolStripMenuItem下再添加子级菜单

场景
在右键菜单ContextMenuStrip下添加子菜单选项可以通过

ContextMenuStrip menuStrip
ToolStripMenuItem mnuChartOption = new ToolStripMenuItem();     //新建菜单项对象
mnuChartOption.Name = "chart_option";
mnuChartOption.Text = "图形选项";
//点击弹出图形选项对话框
mnuChartOption.Click += delegate(object sender, EventArgs e)
   {
                
    };
menuStrip.Items.Add(mnuChartOption);

来实现。但是如果在右键菜单的子菜单选项下再添加子菜单选项，形成二级子菜单。

注：

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实现
ToolStripMenuItem 的子级菜单仍然是ToolStripMenuItem ，主要通过DropDownItems属性来构建关联关系。

构建右键二级子菜单示例代码

 ToolStripMenuItem mnuDirectPrint = new ToolStripMenuItem("直接打印");
        mnuDirectPrint.Name = "directPrint";
        mnuDirectPrint.Text = "直接打印";
        mnuDirectPrint.Click += delegate(object sender, EventArgs e)
        {
            control.DoPrint();
        };

        ToolStripMenuItem mnuPrintPageSet = new ToolStripMenuItem("打印页面设置");
        mnuPrintPageSet.Name = "printPageSet";
        mnuPrintPageSet.Text = "打印页面设置";
        mnuPrintPageSet.Click += delegate(object sender, EventArgs e)
        {
            control.DoPageSetup();
        };

        ToolStripMenuItem mnuPrint = new ToolStripMenuItem();
        mnuPrint.Name = "mnuPrint";
        mnuPrint.Text = "打印";
        mnuPrint.DropDownItems.Add(mnuDirectPrint);
        mnuPrint.DropDownItems.Add(mnuPrintPageSet);

        
        menuStrip.Items.Add(mnuPrint);
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效果