Convert c# HtmlTextWriter page into simple asp.net

Question

Hi, I got an old web page which is written using HtmlTextWriter.

I have some problems to control it. So I wanted to convert that into simple asp.net page.

What is the way to do so? Below is my code:

<%@ Page Language="C#" %>

<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<script language="C#" runat="server">
    protected override void Render(HtmlTextWriter writer)
    {
        Response.Buffer = true;
        Response.ContentEncoding = Encoding.UTF8;

        String number_appl = "20170001";
        String objIntel = "marks";
        String username;
        username = User.Identity.Name;

        writer.WriteFullBeginTag("html");
        writer.WriteLine();

        writer.WriteBeginTag("meta");
        writer.WriteAttribute("http-equiv", "Content-Type");
        writer.WriteAttribute("content", "text/html; charset=utf-8");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteLine();

        writer.WriteBeginTag("xml");
        writer.WriteAttribute("id", "template");
        writer.WriteAttribute("src", "/edit/source.aspx?objIntel=" + objIntel + "&filename=template.xml&un=");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("xml");
        writer.WriteLine();

        writer.WriteBeginTag("xml");
        writer.WriteAttribute("id", "data");
        writer.WriteAttribute("src", "/edit/source.aspx?objIntel=DataBase\\" + objIntel + "&filename=\\xmls\\" + number_appl + ".xml&un=" + username);
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("xml");
        writer.WriteLine();

        writer.WriteBeginTag("xml");
        writer.WriteAttribute("id", "style");
        writer.WriteAttribute("src", "/edit/source.aspx?objIntel=" + objIntel + "&filename=b7b.xsl&un=" + username);
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("xml");
        writer.WriteLine();

        writer.WriteBeginTag("xml");
        writer.WriteAttribute("id", "xmlerror");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteBeginTag("XMLDATA");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("XMLDATA");
        writer.WriteEndTag("xml");
        writer.WriteLine();

        writer.WriteBeginTag("LINK");
        writer.WriteAttribute("REL", "STYLESHEET");
        writer.WriteAttribute("HREF", "/edit/styles.css");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("LINK");
        writer.WriteLine();

        writer.WriteBeginTag("script");
        writer.WriteAttribute("language", "JScript");
        writer.WriteAttribute("src", "/edit/source.aspx?objIntel=" + objIntel + "&filename=showxml.js");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("script");
        writer.WriteLine();
        writer.WriteBeginTag("TITLE");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.Write(number_appl);
        writer.WriteEndTag("TITLE");
        writer.WriteLine();

        writer.WriteBeginTag("body");
        writer.WriteAttribute("alink", "#006666");
        writer.WriteAttribute("Link", "#006666");
        writer.WriteAttribute("Vlink", "#006666");
        writer.WriteAttribute("bgcolor", "#f0fff0");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteLine();

        writer.WriteBeginTag("DIV");
        writer.WriteAttribute("id", "showResult");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("DIV");
        writer.WriteLine();

        writer.WriteBeginTag("FORM");
        writer.WriteAttribute("ENCTYPE=", "multipart/form-data");
        writer.WriteAttribute("action", "savexml.aspx?un=" + username);
        writer.WriteAttribute("method", "POST");

        writer.WriteAttribute("name", "FORM1");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteBeginTag("INPUT");
        writer.WriteAttribute("type", "submit");
        writer.WriteAttribute("name", "Enter");
        writer.WriteAttribute("value", "????????????? ?????????");
        writer.WriteAttribute("onClick", "achSendDataToServer()");
        writer.WriteEndTag("INPUT");
        writer.WriteBeginTag("INPUT");
        writer.WriteAttribute("type", "hidden");
        writer.WriteAttribute("name", "blob");
        writer.WriteAttribute("value", "blob_xml");
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("INPUT");
        writer.WriteBeginTag("INPUT");
        writer.WriteAttribute("type", "hidden");
        writer.WriteAttribute("name", "appl_number");
        writer.WriteAttribute("value", number_appl);
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("INPUT");
        writer.WriteBeginTag("INPUT");
        writer.WriteAttribute("type", "hidden");
        writer.WriteAttribute("name", "vid");
        writer.WriteAttribute("value", objIntel);
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("INPUT");
        writer.WriteBeginTag("INPUT");
        writer.WriteAttribute("type", "hidden");
        writer.WriteAttribute("name", "un");
        writer.WriteAttribute("value", username);
        writer.Write(HtmlTextWriter.TagRightChar);
        writer.WriteEndTag("INPUT");
        writer.WriteEndTag("FORM");
        writer.WriteLine();

        writer.Write("<?xml version=\"1.0\" encoding=\"utf-8\"?> <user name=\"u_name\"> </user>");


        writer.WriteEndTag("body");
        writer.WriteLine();
        writer.WriteEndTag("html");

    }

</script>