DropDownList添加一项默认值？

        //企业选择的网站类别
        DataSet ds_mark_code_common = new Mark_Code_CommonBLL().MARKP_CodeCommon_selectByConditions(CompanyId, 1, 1);
        ddlCommonList.DataSource = ds_mark_code_common;
        ddlCommonList.DataTextField = "MCC_Ccname";
        ddlCommonList.DataValueField = "MCC_Id";
        ddlCommonList.DataBind();

 

          //需要在最后一行，在绑定数据的后面

        ddlCommonList.Items.Insert(0, new ListItem("请选择...", "0"));