title: Add arbitrary route prefix to all attribute routes in webapi 2.2
body: <p>This was kind of asked at <a href="https://stackoverflow.com/questions/22070559/web-api-2-global-route-prefix-for-route-attributes">Web Api 2 global route prefix for route attributes?</a>.</p>
  
  <p>I'm using attribute routing and class level route prefixes already. However, from a configuration of some sort (could be code) I would like to add another prefix to all the attribute routes. I do not want to create custom route attributes to use throughout my code base, just the built in ones.</p>
  
  <p>Is this possible?</p>
  
  <p>Simply put, I would like to take my routes
  /a/1/b/2
  and
  /x/3/y/2/z/1
  and turn them in to (although it doesn't necessarily need to be a /api prefix)
  /api/1/b/2
  and
  /api/x/3/y/2/z/1</p>