richtextbox 复制、粘贴、删除、全选

private void contextMenuStrip_ItemClicked(object sender, ToolStripItemClickedEventArgs e)
        {
            switch (e.ClickedItem.Name)
            {
                case "MenuItemCopy":
                    this.RTBNoticeContent.Copy();
                    break;
                case "MenuItemPaset":
                    this.RTBNoticeContent.Paste();
                    break;
                case "MenuItemCut":
                    this.RTBNoticeContent.Cut();
                    break;
                case "MenuItemDel":
                    this.RTBNoticeContent.SelectedText = "";
                    break;
                case "MenuItemSelAll":
                    this.Focus();
                    this.RTBNoticeContent.SelectAll();
                    break;
            }
        }