i am getting error in my code to generate pdf file from asp.net page

protected void Submitbtn_Click(object sender, EventArgs e)
 {
     {                    Response.ContentType = "application/pdf";
                Response.AddHeader("content-disposition", "attachment;filename=FileName.pdf");
                Response.Cache.SetCacheability(HttpCacheability.NoCache);

                StringWriter sw = new StringWriter();

                HtmlTextWriter w = new HtmlTextWriter(sw);
                print.RenderControl(w)

                string htmWrite = sw.GetStringBuilder().ToString();
                htmWrite = Regex.Replace(htmWrite, "", "");
                htmWrite = htmWrite.Replace("\r\n", "");
                StringReader reader = new StringReader(htmWrite);

                Document doc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
                string pdfFilePath = Server.MapPath(".") + "/PDFFiles";

                HTMLWorker htmlparser = new HTMLWorker(doc);
                PdfWriter.GetInstance(doc, Response.OutputStream);

                doc.Open();
                try
                {

                    htmlparser.Parse(reader);
                    doc.Close();
                    Response.Write(doc);
                    Response.End();
                }
                catch (Exception )
                { }
                finally
                {
                   doc.Close();
                }



        public override void VerifyRenderingInServerForm(Control control)
        {
             /* Verifies that the control is rendered */
        }
}
error shown is
RegisterForEventValidation can only be called during Render();