title: Prevent page from being cached when using OutputCacheAttribute
body: <p>Is there a way to prevent a page from being cached based on some logic?</p>
  
  <p>I want to cache anonymous access to a page, so I can set <code>VaryByCustom="user"</code> and have some magic in Global.asax's <code>GetVaryByCustomString</code> method.  Ok.  But I don't actually want to cache the page if the user's authenticated, only if it's not authenticated.  Is there a way to specify this kind of thing?</p>
  
  <p>The reason I want the data to not be added to the cache to begin with (instead of added with some random key) is that as the cache grows things get thrown out and I don't want the non-authenticated version to get thrown out.</p>