title: IIDentity does not contain a definition for 'GetUserId'
body: <p>I'm trying to use the VS2015 MVC controller and specifically GetUserID on User.Identity </p>
  
  <p>i have seen a number of similar questions relating to this which state to add reference to Microsoft.AspNet.Identity, however as you can see that is referenced.</p>
  
  <p>i assume i'm missing a package or something i just cannot figure it out </p>
  
  <pre><code>using Microsoft.AspNet.Identity;
  using Microsoft.AspNet.Mvc;
  using Web_Test.Models;  
  
  namespace Web_Test.Controllers
  {
      public class TestController : Controller
      {
      public TestController(UserManager&lt;ApplicationUser&gt; userManager, SignInManager&lt;ApplicationUser&gt; signInManager)
      {
          UserManager = userManager;
          SignInManager = signInManager;
      }
      public UserManager&lt;ApplicationUser&gt; UserManager { get; private set; }
      public SignInManager&lt;ApplicationUser&gt; SignInManager { get; private set; }
  
      public IActionResult Index()
      {
          //GetUserId() underlined in Red in VS2015
          //IIDentity does not contain a definition for 'GetUserId'
          string currentUserId = User.Identity.GetUserId();
          return View();
      }
  }
  }
  </code></pre>