Listbox 添加右键菜单

public Form1()
{
            InitializeComponent();

            ContextMenuStrip listboxMenu = new ContextMenuStrip();
            ToolStripMenuItem rightMenu = new ToolStripMenuItem("Copy");
            rightMenu.Click += new EventHandler(Copy_Click);
            listboxMenu.Items.AddRange(new ToolStripItem[] { rightMenu });
            listbox1.ContextMenuStrip = listboxMenu;

            listbox1.Items.Add("1");
            listbox1.Items.Add("2");
            listbox1.Items.Add("3");
            listbox1.Items.Add("4");
}


private void Copy_Click(object sender, EventArgs e)
{
            Clipboard.SetText(listbox1.Items[listbox1.SelectedIndex].ToString());
}