URL Rewriting with ASP.NET

http://www.codeproject.com/KB/aspnet/urlrewriter.aspx
Web.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <sectionGroup name="system.web">
            <section name="urlrewrites" type="ThunderMain.URLRewriter.Rewriter, ThunderMain.URLRewriter, Version=1.0.783.30976, Culture=neutral, PublicKeyToken=7a95f6f4820c8dc3"/>   
        </sectionGroup>
    </configSections>
  <system.web>


        <!--
          
        Maps from old website to new website using Regular Expressions
        rule/url - old website url (Regular Expression)
        rule/rewrite - new website replacement expression
          
        Of two or more rules which match a given request, the first
        will always take precedance.

          
        Created : 2002-02-22 : Richard Birkby
          
        Proposed extra features:
               Cache a number of URL Rewrites
               Allow the rule to determine whether to rewrite the URL, or to redirect the client
           
        -->
        <urlrewrites>
            <rule>
                <url>/urlrewriter/show/.asp</url>
                <rewrite>show.aspx</rewrite>
            </rule>
            <rule>
                <url>/urlrewriter/wohs/.asp</url>
                <rewrite>show.aspx</rewrite>
            </rule>   
            <rule>
                <url>/urlrewriter/show(.*)/.asp</url>
                <rewrite>show.aspx?$1</rewrite>
            </rule>   
            <rule>
                <url>/urlrewriter/(.*)show/.html</url>
                <rewrite>show.aspx?id=$1&amp;cat=2</rewrite>
            </rule>   
            <rule>
                <url>/urlrewriter/s/h/o/w/(.*)/.html</url>
                <rewrite>/urlrewriter/show.aspx?id=$1</rewrite>
            </rule>   
        </urlrewrites>
           
   
    <!--  DYNAMIC DEBUG COMPILATION
          Set compilation debug="true" to enable ASPX debugging.  Otherwise, setting this value to
          false will improve runtime performance of this application.
          Set compilation debug="true" to insert debugging symbols (.pdb information)
          into the compiled page. Because this creates a larger file that executes
          more slowly, you should set this value to true only when debugging and to
          false at all other times. For more information, refer to the documentation about
          debugging ASP .NET files.
    -->
    <compilation
         defaultLanguage="c#"
         debug="true"
    />

    <!--  CUSTOM ERROR MESSAGES
          Set customError mode values to control the display of user-friendly
          error messages to users instead of error details (including a stack trace):

          "On" Always display custom (friendly) messages 
          "Off" Always display detailed ASP.NET error information.
          "RemoteOnly" Display custom (friendly) messages only to users not running
          on the local Web server. This setting is recommended for security purposes, so
          that you do not display application detail information to remote clients.
    -->
    <customErrors
    mode="RemoteOnly"
    />

    <!--  AUTHENTICATION
          This section sets the authentication policies of the application. Possible modes are "Windows", "Forms",
          "Passport" and "None"
    -->
    <authentication mode="Windows" />

    <!--  APPLICATION-LEVEL TRACE LOGGING
          Application-level tracing enables trace log output for every page within an application.
          Set trace enabled="true" to enable application trace logging.  If pageOutput="true", the
          trace information will be displayed at the bottom of each page.  Otherwise, you can view the
          application trace log by browsing the "trace.axd" page from your web application
          root.
    -->
    <trace
        enabled="false"
        requestLimit="10"
        pageOutput="false"
        traceMode="SortByTime"
        localOnly="true"
    />

    <!--  SESSION STATE SETTINGS
          By default ASP .NET uses cookies to identify which requests belong to a particular session.
          If cookies are not available, a session can be tracked by adding a session identifier to the URL.
          To disable cookies, set sessionState cookieless="true".
    -->
    <sessionState
            mode="InProc"
            stateConnectionString="tcpip=127.0.0.1:42424"
            sqlConnectionString="data source=127.0.0.1;user id=sa;password="
            cookieless="false"
            timeout="20"
    />

    <!--  GLOBALIZATION
          This section sets the globalization settings of the application.
    -->
    <globalization
            requestEncoding="utf-8"
            responseEncoding="utf-8"
   />
  
 </system.web>

</configuration>
============
Show.aspx
<%@ Page language="c#"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
    <head>
        <title>Show</title>
    </head>
    <body>

        <script runat="server">
            static int x=1;

            private void Page_Load(object sender, System.EventArgs e) {
                Response.Write("Page= <b>" + Request.Url + "</b><br> called " + x + " times" );
                x++;
            }
        </script>

    </body>
</html>
===========
Rewriter.cs
using System;
using System.Web;
using System.Xml;
using System.Xml.XPath;
using System.Configuration;
using System.Collections.Specialized;
using System.Text.RegularExpressions;
using System.Xml.Xsl;
using System.Reflection;
using System.Runtime.CompilerServices;

[assembly: AssemblyDelaySign(false)]
[assembly: AssemblyKeyFile(@"keyfile.snk")]
[assembly: AssemblyKeyName("")]
[assembly: AssemblyVersion("1.0.783.30976")]


namespace ThunderMain.URLRewriter {

    public class Rewriter : IConfigurationSectionHandler {
        protected XmlNode _oRules=null;

        protected Rewriter(){}

        public string GetSubstitution(string zPath) {
            Regex oReg;

            foreach(XmlNode oNode in _oRules.SelectNodes("rule")) {
                oReg=new Regex(oNode.SelectSingleNode("url/text()").Value);
                Match oMatch=oReg.Match(zPath);

                if(oMatch.Success) {
                    return oReg.Replace(zPath,oNode.SelectSingleNode("rewrite/text()").Value);
                }
            }

            return zPath;
        }

        public static void Process() {
            Rewriter oRewriter=(Rewriter)ConfigurationSettings.GetConfig("system.web/urlrewrites");


            string zSubst=oRewriter.GetSubstitution(HttpContext.Current.Request.Path);


            if(zSubst.Length>0) {
                HttpContext.Current.RewritePath(zSubst);
            }
        }

        #region Implementation of IConfigurationSectionHandler
        public object Create(object parent, object configContext, XmlNode section) {           
            _oRules=section;

            // TODO: Compile all Regular Expressions

            return this;
        }
        #endregion
    }
}
===========
Make Rewriter.bat
@Echo Off

csc /target:library /out:bin/ThunderMain.URLRewriter.dll rewriter.cs
Echo Compilation Complete
Echo.
Echo Now install into the GAC by dragging and dropping bin/ThunderMain.URLRewriter.dll into C:/Windows/assembly
Echo.
pause
============
default.aspx
<%@ Page language="c#" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
    <HEAD>
        <title>default</title>

    </HEAD>
    <body>
        <form id="default" method="post" runat="server">
            <UL>
                <LI>
                    <A href="show.asp">show.asp</A>
                <LI>
                    <A href="wohs.asp">wohs.asp</A>
                <LI>
                    <A href="show5.asp">show5.asp</A>
                <LI>
                    <A href="42show.html">42show.html</A>
                <LI>
                    <A href="s/h/o/w/5.html">s/h/o/w/5.html</A></LI></UL>
            <P>&nbsp;</P>
        </form>
    </body>
</HTML>
===================
Global.asax
<%@Assembly Name="ThunderMain.URLRewriter" %>

<script language="C#" runat="server">
    protected void Application_BeginRequest(Object sender, EventArgs e){
        ThunderMain.URLRewriter.Rewriter.Process();
    }
</script>