title: Finding all uses of a Custom Attribute and retrieving the values
body: <p>I have an MVC4 app with multiple controllers that all inherit from BaseController.  In some of these controllers, I have Actions with a Custom Attribute of PageKey.  Page Key has two properties (Group &amp; Key).  </p>
  
  <p>I need a way to get every instance of this attribute in all controllers and access the values.  I also want to not have to modify the code later when I add new controllers or instances of the attribute.</p>