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I am creating Pdf file from dataset for first time i can create pdf but for the secnd time its giving me this error

here is my code

for first tim its going to rendercontrol and for the secnd time its giving me this error

public void Email()
    {
        try
        {
            emaildata();
            string userMail = emailname + "@ksmc.med.sa";
            using (StringWriter sw = new StringWriter())
            {
                using (HtmlTextWriter hw = new HtmlTextWriter(sw))
                {
                    DetailsView1.RenderControl(hw);
                    StringReader sr = new StringReader(sw.ToString());
                    Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 0f);
                    HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        PdfWriter.GetInstance(pdfDoc, memoryStream);
                        pdfDoc.Open();
                        htmlparser.Parse(sr);
                        pdfDoc.Close();
                        byte[] bytes = memoryStream.ToArray();
                        memoryStream.Close();
                     }
                 }
           }
        }
}

public void emaildata()
   {
       SqlCommand cmnd = new SqlCommand("SELECT dbo.Tbl_TechRequest.R_RequestNumber, dbo.Tbl_TechRequest.R_name, FROM _TechRequest WHERE  (dbo.Tbl_TechRequest.R_RequestNumber" +
            "   =@R_RequestNumber)");
       cmnd.Connection = con;
       cmnd.Parameters.Add("@R_RequestNumber", SqlDbType.Int).Value = id;
       SqlDataAdapter da = new SqlDataAdapter(cmnd);

       da.Fill(ds);
       DetailsView1.DataSource = ds;
       DetailsView1.DataBind();
   }