Url Rewriting for dynamic subdomain, without any entry in DNS

Step 1: Add UrlRewriting Class in App_Code

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using System.Web;
public class UrlRewriting : IHttpModule
{
    public void Init(HttpApplication app)
    {
        app.BeginRequest += ppBeginRequest;
        app.EndRequest += ppEndRequest;
    }
    public void Dispose()
    {
    }


    public void ppBeginRequest(object s, EventArgs e)
    {
        HttpApplication app = default(HttpApplication);
        string[] urlArr = null;
        app = (HttpApplication)s;
        string strHostDomain = app.Context.Request.ServerVariables["SERVER_NAME"];


        urlArr = strHostDomain.Split('.');
        if (urlArr.Length == 3)
        {
            if (urlArr[0].Substring(0, 3) == "www")
            {
                // do nothing here .. normal site
            }


            // Subdomain Blogs: http://blogs.mysite.com 
            if (urlArr[0].Substring(0, 3) == "blogs")
            {
                app.Context.RewritePath("/blogs/Default.aspx");
                // app.Context.Request.Url.PathAndQuery = if you need the querystring
            }


            // Subdomain Blogs: http://photosite.mysite.com 
            if (urlArr[0].Substring(0, 3) == "photosite")
            {
                app.Context.RewritePath("/photosite/Default.aspx");
                // app.Context.Request.Url.PathAndQuery = if you need the querystring
            }
        }
    }


    public void ppEndRequest(object s, EventArgs e)
    {
    }
}

Step 2: Add this part in web.config

<system.web>
    <compilation debug="true" targetFramework="4.0"/>
    <httpModules>
      <add name="UrlRewriting" type="UrlRewriting"/>
    </httpModules>
  </system.web>