title: IRequiresSessionState vs IReadOnlySessionState
body: <p>What is the difference between <code>IRequiresSessionState</code> and <code>IReadOnlySessionState</code> beside the inability of the second to save changes to the session variables?  </p>
  
  <p>Both provide me the ability to access session variables in my <code>HttpHandler</code>. But why would I prefer <code>IReadOnlySessionState</code>? It just restricts me from saving the session for the next request.<br>
  Or does it gives me an performance advantage over <code>IRequiresSessionState</code>?</p>
  
  <p>When would I prefer to use <code>IReadOnlySessionState</code> over <code>IRequiresSessionState</code>?</p>