title: how can I get Identity UserID in the controller right after a successful login result?
body: <p>I am using Identity v2 and MVC 5 for external login.</p>
  
  <p>In my external login callback function, I log the user in with </p>
  
  <pre><code>var result = await SignInManager.ExternalSignInAsync(loginInfo, isPersistent: false);
  </code></pre>
  
  <p>then there is a switch for the <code>result</code>, and I need to access the user's ID in the <code>success</code> case, but <code>User.Identity.GetUserId();</code> gives me null here.</p>
  
  <p>How can I access the User's ID in this case?</p>