Getting Error While Converting aspx to pdf

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C#

VB

ASP.NET

The error is Unable to cast object of type "'iTextSharp.text.html.simpleparser.CellWrapper' to type 'iTextSharp.text.Paragraph'". Plese dont duplicate i couldnot find the solution.
Please Help

Response.ContentType = "application/pdf";
        Response.AddHeader("content-disposition", "attachment;filename=Panel.pdf");
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        StringWriter sw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(sw);
        pnlPerson.RenderControl(hw);
        gridstudentnotes.DataBind();

        StringReader sr = new StringReader(sw.ToString());
        Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
        HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
        PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
        pdfDoc.Open();
        htmlparser.Parse(sr);
        pdfDoc.Close();
        Response.Write(pdfDoc);
        Response.End();