如何将选定的网格视图详细信息转换为pdf?得到错误

代码1:

private void GetPaymentReport()
        {
            try
            {
                string todate = txttodate.Text;
                string[] todatesplt = todate.Split('-');
                int todatemnth = Convert.ToInt32(todatesplt[0]);
                int todatedate = Convert.ToInt32(todatesplt[1]);
                int todateyr = Convert.ToInt32(todatesplt[2]);
                string fromdate = txtfromdate.Text;
                string[] frmdatesplt = fromdate.Split('-');
                int frmdatemnth = Convert.ToInt32(frmdatesplt[0]);
                int frmdatedate = Convert.ToInt32(frmdatesplt[1]);
                int frmdateyr = Convert.ToInt32(frmdatesplt[2]);
                DateTime start = new DateTime(frmdateyr, frmdatemnth, frmdatedate);
                DateTime end = new DateTime(todateyr, todatemnth, todatedate);
                int loanpaymentid = Convert.ToInt32(Session["Loanid"].ToString());
                var query = from p in mortgageentity.Payments
                            join D in mortgageentity.Debit_Method on p.Debit_Method_ID equals D.Debit_Method_ID
                            join pt in mortgageentity.Payment_Type on p.Payment_Type_ID equals pt.Payment_Type_ID
                            where (p.Client_Pmt_Date >= start) && (p.Client_Pmt_Date <= end) && (p.Loan_ID == loanpaymentid)orderby p.Client_Pmt_Date descending
                            select new
                            {
                                p.Pmt_ID,
                                p.Loan_ID,
                                p.Client_Pmt_Date,
                                p.MtgSvr_Pmt_Start_Date2,
                                D.Debit_Method_Desc,
                                p.Total_Debit_Amt,
                                p.CreditAmt,
                                p.LenderAmt,
                                pt.Payment_Type_Desc,
                                p.Return_Code,
                                p.Returned_Date
                            };
                grdviewPayments.DataSource = query.ToList();
                grdviewPayments.DataBind();
            }
            catch { }
        }

代码2:

protected void btnemail_Click(object sender, EventArgs e)
       {
    Response.ContentType = "application/pdf";
           Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.pdf");
           Response.Cache.SetCacheability(HttpCacheability.NoCache);
           StringWriter sw = new StringWriter();
           HtmlTextWriter hw = new HtmlTextWriter(sw);
           grdviewPayments.AllowPaging = false;
           grdviewPayments.DataBind();
           grdviewPayments.RenderControl(hw);
           StringReader sr = new StringReader(sw.ToString());
           Document pdfDoc = new Document(PageSize.A4,10f,10f,10f,0f);
           HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
           PdfWriter.GetInstance(pdfDoc,Response.OutputStream);
           pdfDoc.Open();
           htmlparser.Parse(sr);
           pdfDoc.Close();
           Response.Write(pdfDoc);
           Response.End();
      }

如上所述，我有code1从gridview格式的数据库中获取数据，code2将gridview数据转换为PDF格式。但我的问题是得到错误，如"控制'ctl00_ContentPlaceHolder1_TabContainer1_TabPanel1_Paymentreport_grdviewPayments'类型'GridView'必须放置在一个表单标签与runat=server."在code2位置:grdviewPayments.RenderControl(hw);

请帮帮我。问候。

StringBuilder sb = new StringBuilder();
StringWriter tw = new StringWriter(sb);
HtmlTextWriter hw = new HtmlTextWriter(tw);
grdviewPayments.RenderControl(hw);
StringReader sr = new StringReader(hw.ToString());