Object reference not set to an instance of an object. Error

Question

Hello,

 

I am developing a project, in that project i want that, after submitting the data, user can generate pdf of that data. I enclosed the data into a panel to generate a pdf. On Generating pdf i am getting an error, and it is 

Object reference not set to an instance of an object.

 my onbuttonclick function is like:

 

protected void btnPdf_Click(object sender, EventArgs e)

{

btnUpload.Visible = false;

FileUpload1.Visible = false;

string attachment = "attachment; filename=" + "abc" + ".pdf";

Response.ClearContent();

Response.AddHeader("content-disposition", attachment);

Response.ContentType = "application/pdf";

StringWriter s_tw = new StringWriter();

HtmlTextWriter h_textw = new HtmlTextWriter(s_tw);

h_textw.AddStyleAttribute("font-size", "7pt");

h_textw.AddStyleAttribute("color", "Black");

Panel1.RenderControl(h_textw);//Name of the Panel

Document doc = new Document();

doc = new Document(PageSize.A4, 5, 5, 15, 5);

//FontFactory.GetFont("Verdana", 80, iTextSharp.text.Color.RED);

//FontFactory.GetFont("Verdana", 80, iTextSharp.text.BaseColor.RED);

PdfWriter.GetInstance(doc, Response.OutputStream);

doc.Open();

StringReader s_tr = new StringReader(s_tw.ToString());

HTMLWorker html_worker = new HTMLWorker(doc);

html_worker.Parse(s_tr);

doc.Close();

Response.Write(doc);

}

 

Please help me to resolve this error..

 

Thank You...