Search Engine Optimization(SEO) and URL Rewriting using HTTPModules - Microsoft ASP.NET

Implement IHttpModule interface, which has Initialization(public void Init(HttpApplication context)) methods. In there we attach URL Rewrite method to AuthorizeRequest (for windows authorization)
Note:This is a simplified version. For more information please see references at the end of this post.

namespace Root.Client.SEOHandler
{
    public class SEOModule : IHttpModule
    {
        public void Init(HttpApplication context)
        {
            context.AuthorizeRequest += new EventHandler(SEOModuleAuthorizeRequest);
        }
        public void SEOModuleAuthorizeRequest(object sender, EventArgs e)
        {
            HttpApplication app = (HttpApplication)sender;
            /// 
            ///we must implement switches collection in CustomConfiguration as a property. 
            ///See complete description of how to implement a custom configuration 
            ///section in web.config please see 
            ///Adding new section to web.config - Microsoft ASP.NET
            ///
            List<Switch> switches =((CustomConfiguration) HttpContext.Current.Cache ["customConfiguration"]).Switches;
            for (int i = 0; i < switches.Count; i++)
            {
                string lookFor = string.Format("{0}/{1}",app.Context.Request.ApplicationPath,switches[i]);
                if(string.Compare(lookFor,app.Request.Path)==0)
                app.Context.RewritePath(
                string.Format("{0}/{1}","required_page.aspx", app.Context.Request.ApplicationPath);
            }
        }
    }
}

Register assembly in web.config

<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
  <system.web>
    <httpModules>
      <add name="SEOModule" type="Root.Client.SEOHandler.SEOModule" />
    </httpModules>
  </system.web>
</configuration>

Reference: URL Rewriting in ASP.NET