title: 'System.Web.HttpContext' does not contain a definition for 'GetOwinContext'
body: <p>I have the following error :'System.Web.HttpContext' does not contain a definition for 'GetOwinContext' 
  whenever I debug my project. this error is in the web API page, although it doesn't show an error in the default AccounController.cs and the nuget package is installed.what is missing?</p>
  
  <pre><code>using IdentitySample.Models;
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Net;
  using System.Net.Http;
  using System.Web.Http;
  using Microsoft.AspNet.Identity;
  using Microsoft.AspNet.Identity.Owin;
  using Microsoft.Owin.Security;
  using System.Web;
  using System.Threading.Tasks;
  using task.Models;
  using System.Globalization;
  public ApplicationUserManager UserManager
      {
          get
          {
              return _userManager ?? HttpContext.GetOwinContext().GetUserManager&lt;ApplicationUserManager&gt;();
  
          }
          private set
          {
              _userManager = value;
          }
      }
  </code></pre>