title: OnAuthorization vs AuthorizeCore
body: <p>I am from visaul basic background and newly entered into asp.net mvc world. So,
  kindly bear with me if question sound small.
  I need to implement custom authorize attribute and have seen various samples overriding 'OnAuthorization' or 'AuthorizeCore'. Also have read that we should 
  not override 'OnAuthorization' because it stores result in cache. But really didn't understand actual difference between them.</p>
  
  <p>Can you please provide me some link that shows when to override any of them or
  whether we can use both simultaneously.</p>
  
  <p>thanks
  Arun</p>