Devexpress DropDownButton 用法

 public partial class XtraForm2 : DevExpress.XtraEditors.XtraForm    {        public XtraForm2()        {            InitializeComponent();            CreateDropDownControl();        }        private void CreateDropDownControl()        {            DropDownButton btn = new DropDownButton();            btn.Text = "Click here";            btn.DropDownControl = CreateDXPopupMenu();            btn.Location = new Point(100, 200);            Controls.Add(btn);        }        private DXPopupMenu CreateDXPopupMenu()        {            DXPopupMenu menu = new DXPopupMenu();            menu.Items.Add(new DXMenuItem("Item", OnItemClick));            menu.Items.Add(new DXMenuCheckItem("CheckItem", false, null, OnItemClick));            DXSubMenuItem subMenu = new DXSubMenuItem("SubMenu");            subMenu.Items.Add(new DXMenuItem("SubItem", OnItemClick));            menu.Items.Add(subMenu);            return menu;        }        private void OnItemClick(object sender, EventArgs e)        {            DXMenuItem item = sender as DXMenuItem;            XtraMessageBox.Show(item.Caption);        }    }