I followed all the instructions on this link.

Convert HTML to PDF with CSS using iText7 in ASP.Net

tr:nth-child(even) and tr:nth-child(odd) not reflecting in IText7 exported pdf, It only reflects on the apsx page not pdf.

is there any other way to add this effect

My code

CSS

StyleSheet .css 
#tableDetails {
    font-family: Arial;
    font-size: 8px;
    width: 200px;
border: 1px solid black;

}
 
.header {
    background-color: #18B5F0;
    height: 18px;
    color: black;
    border: 1px solid white;
    text-align: center;
}
.div {
    background-color: #18B5F0;
    height: 18px;
    color: black;
    border: 1px solid white;
    text-align: center;
}

tr:nth-child(even) {
    background-color: #D1DDF1
}
 
tr:nth-child(odd) {
    background-color: #EFF3FB
}

HTML

<div>
    <link href="StyleSheet.css" rel="stylesheet" />
    <asp:Panel ID="pnlPerson" runat="server">
        <table border="1" class="tableDetails">
            <tr>
                <td colspan="2" class="header">
                    <b>Personal Details</b>
                </td>
            </tr>
            <tr>
                <td><b>Name</b></td>
                <td>
                    <asp:Label ID="lblName" runat="server"></asp:Label></td>
            </tr>
            <tr>
                <td><b>Age</b></td>
                <td>
                    <asp:Label ID="lblAge" runat="server"></asp:Label></td>
            </tr>
            <tr>
                <td><b>City</b></td>
                <td>
                    <asp:Label ID="lblCity" runat="server"></asp:Label></td>
            </tr>
            <tr>
                <td><b>Country</b></td>
                <td>
                    <asp:Label ID="lblCountry" runat="server"></asp:Label></td>
            </tr>
        </table>
    </asp:Panel>
    <asp:Button ID="btnExport" runat="server" Text="Export" OnClick="btnExport_Click" />
</div>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        //Populate DataTable
        DataTable dt = new DataTable();
        dt.Columns.Add("Name");
        dt.Columns.Add("Age");
        dt.Columns.Add("City");
        dt.Columns.Add("Country");
        dt.Rows.Add();
        dt.Rows[0]["Name"] = "Mudassar Khan";
        dt.Rows[0]["Age"] = "27";
        dt.Rows[0]["City"] = "Mumbai";
        dt.Rows[0]["Country"] = "India";

        //Bind Datatable to Labels
        lblName.Text = dt.Rows[0]["Name"].ToString();
        lblAge.Text = dt.Rows[0]["Age"].ToString();
        lblCity.Text = dt.Rows[0]["City"].ToString();
        lblCountry.Text = dt.Rows[0]["Country"].ToString();
    }
}
protected void btnExport_Click(object sender, EventArgs e)
{
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
    pnlPerson.RenderControl(hw);
    StringReader sr = new StringReader(sw.ToString());
    Document pdfDoc = new Document();
    PdfWriter PdfWriter = PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
    HtmlPipelineContext htmlContext = new HtmlPipelineContext(null);
    htmlContext.SetTagFactory(Tags.GetHtmlTagProcessorFactory());
    ICSSResolver cssResolver = XMLWorkerHelper.GetInstance().GetDefaultCssResolver(false);
    cssResolver.AddCssFile(Server.MapPath("~/StyleSheet.css"), true);
    IPipeline pipeline = new CssResolverPipeline(cssResolver, new HtmlPipeline(htmlContext, new PdfWriterPipeline(pdfDoc, PdfWriter)));
    var worker = new XMLWorker(pipeline, true);
    var xmlParse = new XMLParser(true, worker);
    pdfDoc.Open();
    xmlParse.Parse(sr);
    xmlParse.Flush();
    pdfDoc.Close();
    Response.ContentType = "application/pdf";
    Response.AddHeader("content-disposition", "attachment;filename=Panel.pdf");
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    Response.Write(pdfDoc);
    Response.End();
}

Why is the css not applying to the pdf?

Please help.