title: Fastest way to rewrite only one subpath
body: <p>I have a website developed in Classic ASP.NET and running on IIS 7.5. It works okay. But now I have the task to add affiliate program to my website. I want my reflink to looks like <code>www.mywebsite.com/r/userid</code>. Well, I googled around and found I can:</p>
  
  <ol>
  <li><p>Use UrlRewrite third-party <code>HttpModule</code>s. As I understand, they are based on <code>runAllManagedModulesForAllRequests="true"</code> web.config setting. Theoretically, I can:</p></li>
  <li><p>Set <code>runAllManagedModulesForAllRequests="true"</code> and do <code>RewritePath</code> in <code>Application_BeginRequest</code> manually. But my <code>Application_BeginRequest</code> already contains a bit of code. It is too heavy to send all pages, images etc. to <code>Application_BeginRequest</code> because of one rarely called URL.</p></li>
  </ol>
  
  <p>So, the question is how can I rewrite only subpath that starts with <code>www.mywebsite.com/r/</code>, and do not call  <code>Application_BeginRequest</code> for every image, css etc.? Best if no third-party things.</p>