使用iTextSharp不会应用CSS样式

Question

我正在使用iTextSharp创建PDF文档，但我的CSS样式未应用，特别是背景颜色。

protected void btnMail_Click(object sender, EventArgs e)
{
    Response.Clear();
    try
    {
        if (Session["Projectname"] != null && Session["Projectname"].ToString() != string.Empty)
        {
            string Projname = Session["Projectname"].ToString();
            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment;filename=" + Projname + ".pdf");
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            System.IO.StringWriter stringWrite = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
            design.RenderControl(htmlWrite);
            StringReader sr = new StringReader(stringWrite.ToString());
            Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
            HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
            PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
            string strBuilder = stringWrite.ToString();
            string strPath = Request.PhysicalApplicationPath + "\\Temp\\WeeklyReport of " + Projname + ".pdf";
            PdfWriter writer = PdfWriter.GetInstance(pdfDoc, new FileStream(strPath, FileMode.Create));
            pdfDoc.Open();
            htmlparser.Parse(sr);
            pdfDoc.Close();
            pdfDoc.Dispose();
           Response.Write(pdfDoc);
            LblNoteMsg.Text = strPath;
            DateTime input = DateTime.Now;
            int delta = DayOfWeek.Monday - input.DayOfWeek;
            DateTime dats = DateTime.Now.AddDays(delta);
            DateTime monday = input.AddDays(delta);
            string MonDate = monday.ToShortDateString();
            DateTime sat = monday.AddDays(5);
            string SatDate = sat.ToShortDateString();
            StreamReader r = new StreamReader(Server.MapPath("~/WeeklyMail.txt"));
            string body = r.ReadToEnd();
            MailMessage Msg = new MailMessage();
            string MailId = txtMailId.Text;
            foreach (string ss in MailId.Split(",".ToCharArray()))
            {
                if (string.IsNullOrEmpty(ss) == false)
                {
                    Msg.To.Add(new MailAddress(ss));
                }
            }
        }
    }
}