1.Load 事件中注册鼠标点击事件：

(wnText1.OriginControl as WnTextEditorBase).TextEdit.MouseClick += WnFormDemo_MouseClick;

2.拷贝一下方法：

private static void InitRichTextBoxContextMenu(RichTextBox textBox)
        {
            //创建剪切子菜单
            var cutMenuItem = new MenuItem("剪切");
            cutMenuItem.Click += (sender, eventArgs) => textBox.Cut();

            //创建复制子菜单
            var copyMenuItem = new MenuItem("复制");
            copyMenuItem.Click += (sender, eventArgs) => textBox.Copy();

            //创建粘贴子菜单
            var pasteMenuItem = new MenuItem("粘贴");
            pasteMenuItem.Click += (sender, eventArgs) => textBox.Paste();

            //创建右键菜单并将子菜单加入到右键菜单中
            var contextMenu = new ContextMenu();
            contextMenu.MenuItems.Add(cutMenuItem);
            contextMenu.MenuItems.Add(copyMenuItem);
            contextMenu.MenuItems.Add(pasteMenuItem);

            textBox.ContextMenu = contextMenu;
        }

3.调用

private void WnFormDemo_MouseClick(object sender, MouseEventArgs e)
       {
           InitRichTextBoxContextMenu((wnText1.OriginControl as WnTextEditorBase).TextEdit);
       }