สอบถามเรื่องการ Export PDF ครับตอนนี้มีปัญหางงมากครับ

                Dim pdfDoc As New Document(PageSize.A2, 10.0F, 10.0F, 10.0F, 0.0F)
                Dim htmlparser As New HTMLWorker(pdfDoc)
                PdfWriter.GetInstance(pdfDoc, Response.OutputStream)

Protected Sub ExportToPDF(sender As Object, e As EventArgs)
    Using sw As New StringWriter()
        Using hw As New HtmlTextWriter(sw)
            'To Export all pages
            GridView1.AllowPaging = False
            Me.BindGrid()
 
            GridView1.RenderControl(hw)
            Dim sr As New StringReader(sw.ToString())
            Dim pdfDoc As New Document(PageSize.A2, 10.0F, 10.0F, 10.0F, 0.0F)
            Dim htmlparser As New HTMLWorker(pdfDoc)
            PdfWriter.GetInstance(pdfDoc, Response.OutputStream)
            pdfDoc.Open()
            htmlparser.Parse(sr)
            pdfDoc.Close()
 
            Response.ContentType = "application/pdf"
            Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.pdf")
            Response.Cache.SetCacheability(HttpCacheability.NoCache)
            Response.Write(pdfDoc)
            Response.[End]()
        End Using
    End Using
End Sub