要添加一个项目，你会打电话

To add an item, you would call

myContextMenuStrip.Items.Add("Item title", null, myClickHandler);

要增加一个子菜单，你把现有项目和做同样的吧：

To add a sub-menu, you take an existing item and do the same to it:

(myContextMenuStrip.Items[0] as ToolStripMenuItem).DropDownItems.Add(...)