该文档在asp.net中没有页面

Question

我在使用iTextsharp ASP.NET的pdf导出中遇到问题。

错误说明：文档没有页面，pdfdoc.close（）;

这是我的代码：

protected void btnpdf_Click(object sender, EventArgs e)
{
    Response.ContentType = "application/pdf";
    Response.AddHeader("content-disposition",
     "attachment;filename=ProduktivitasReport.pdf");
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
    GridView1.AllowPaging = false;
    GridView1.DataBind();
    GridView1.RenderControl(hw);
    StringReader sr = new StringReader(sw.ToString());
    Document pdfDoc = new Document(PageSize.A4.Rotate(), 10f, 10f, 10f, 0f);
    HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
    PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
    pdfDoc.Open();
    htmlparser.Parse(sr);
    pdfDoc.Close();
    Response.Write(pdfDoc);
    Response.End(); 
}

如何解决这个问题？感谢