Re:Asp.net code to Export gridview to Pdf

protected void Button4_Click(object sender, EventArgs e)
    {
        Response.ContentType = "application/pdf";

        Response.AddHeader("content-disposition",

         "attachment;filename=GridViewExport.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, 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();

       
    }
    public override void VerifyRenderingInServerForm(Control control)
    {

        /* Verifies that the control is rendered */

    }