How can I display all gridview columns in itextsharp?

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C#

Gridview

itextsharp

I have this code for downloading the gridview into a pdf file. My Problem is that it only Downloads the column that are visible. The other columns have values too, they are just not visible.

My Question is: how to show all the columns in the gridview with data and hide the columns that are empty.

public override void VerifyRenderingInServerForm(Control control)
{

}

protected void btnGenerate_Click(object sender, EventArgs e)
{

    string FilePath = MapPath("~/File/doc.pdf");


    iTextSharp.text.Document pdfDoc = new iTextSharp.text.Document(iTextSharp.text.PageSize.A4, 20f, 20f, 20f, 20f);
    PdfWriter.GetInstance(pdfDoc, new FileStream(FilePath, FileMode.Create));
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);

    GridView1.AllowPaging = false;
    GridView1.HeaderRow.Cells[1].Text = "Titel";
    GridView1.HeaderRow.Font.Bold = true;
    GridView1.RenderControl(hw);

    StringReader sr = new StringReader(sw.ToString());
    HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
    PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
    pdfDoc.Open();
    htmlparser.Parse(sr);
    pdfDoc.Close();

    Response.Write(pdfDoc);

    Response.ContentType = "Application/pdf";
    Response.WriteFile(FilePath);
    Response.End();
  }

What I have tried:

Unfortunately nothing came to my mind