导出到word时，怎么添加页眉页脚

        string FileName = “sssssss.doc”;        HttpContext.Current.Response.Charset = "GB2312";        HttpContext.Current.Response.ContentEncoding = Encoding.UTF8;        HttpContext.Current.Response.ContentType = "application/ms-winword";        HttpContext.Current.Response.AppendHeader("Content-disposition", "attachment;filename=" + HttpUtility.UrlEncode(FileName, Encoding.UTF8).ToString());        //HttpContext.Current.Response.        //Lb_Const[0][10].Page.EnableViewState = false;        StringWriter sw = new StringWriter();        HtmlTextWriter tw = new HtmlTextWriter(sw);        //Label lb = null;        //lb = (Label)this.Page.FindControl("Label1");        //if (lb != null) { lb.RenderControl(tw); }        this.Label1.RenderControl(tw);        string css_txt = "<style>" + Css_read() + "</style>";        HttpContext.Current.Response.Write(sw.ToString());        HttpContext.Current.Response.End();