title: MVC Lock and unlock session on one call
body: <p>There is a special behavior I would like to achieve in MVC 5.</p>
  
  <p>I have an ajax call that start after page load that call a slow third party API.
  The flow goes like this:</p>
  
  <ol>
  <li>Controller receive the call.</li>
  <li>Controller access some session ressources.</li>
  <li>Controller call third party API.</li>
  <li>Controller update session variables.</li>
  <li>Controller answer request.</li>
  </ol>
  
  <p>I can't return information to the client since it contains sensitive data so I can't make this in seperates calls to hold data on the client side and then call third party api on a stateless action because I would have to return results of the call to the client to afterwhile make session updates.</p>
  
  <p>This is what I would like to acheive:</p>
  
  <ol>
  <li>Controller receive the call.</li>
  <li>Controller access some session ressources.</li>
  <li>Unlock sessions to allow cocurent calls to access it.</li>
  <li>Controller call third party API.</li>
  <li>Lock session and update session variables.</li>
  <li>Controller answer request.</li>
  </ol>
  
  <p>Is it acheivable?</p>
  
  <p>Thanks for your help.</p>