asp.net datalist绑定数据后可以上移下移

if (e.CommandName == "Up")

        {

            int index = e.Item.ItemIndex;

            string TitleID = rgZdgz.MasterTableView.DataKeyValues[index]["TitleID"].ToString().Trim();
            if (e.Item.ItemIndex > 0)

            {

                ZdgzTitles.ZdgzTitlesDisPlayNum(rgZdgz.MasterTableView.DataKeyValues[index]["TitleID"].ToString().Trim(),

                                        rgZdgz.MasterTableView.DataKeyValues[index-1]["TitleID"].ToString().Trim());

                Clear();

                rgZdgz.Rebind();

            }

            else

            {

                ShowMessage("该项已经在最上，无法再上移。");

            }

        }

        else if (e.CommandName == "Down")

        {

            int index = e.Item.ItemIndex;

            string TitleID = rgZdgz.MasterTableView.DataKeyValues[index]["TitleID"].ToString().Trim();
            if (e.Item.ItemIndex < rgZdgz.Items.Count - 1)

            {

                ZdgzTitles.ZdgzTitlesDisPlayNum(rgZdgz.MasterTableView.DataKeyValues[index]["TitleID"].ToString().Trim(),

                                                rgZdgz.MasterTableView.DataKeyValues[index+1]["TitleID"].ToString().Trim());

                Clear();

                rgZdgz.Rebind();

            }

            else

            {

                ShowMessage("该项已经在最下，无法再下移。");

            }