title: Session variables disappear between requests when using SessionStateBehavior.ReadOnly
body: <p>Very weird behavior.</p>
  
  <p>In my controller I have added an attribute <code>[SessionState(SessionStateBehavior.ReadOnly)]</code> to be able to handle parallel requests.</p>
  
  <p>When added the attribute I see that between requests I lose my session variables. I have seen that the session variables are getting updated, but are lost somewhere along the way.</p>
  
  <p>I have added some debug logs in a couple of life cycle events:</p>
  
  <pre><code>Reqeust1:
  Application_PreRequestHandlerExecute: Session.Count:0
  Application_PostRequestHandlerExecute: Session.Count:3
  
  Reqeust2
  Application_PreRequestHandlerExecute: Session.Count:0
  Application_PostRequestHandlerExecute: Session.Count:0
  </code></pre>
  
  <p>Using <code>.NetFrameWork 4.5.2</code>, <code>Microsoft.AspNet.Mvc.5.2.3</code></p>