title: The entity type IdentityUser is not part of the model for the current context
body: <p>I see the same issue as <a href="https://stackoverflow.com/questions/23914658/owin-oauth-provider-the-entity-type-identityuser-is-not-part-of-the-model-for-t">this</a> question, but the scenario presented there doesn't seem to apply so I think I have a different issue. In fact, I'm seeing several questions on SO that are similar, each with different causes and solutions, so I think this error must be caused from a high level. That said...</p>
  <p>I have an EF code-first database model and I'm trying to use <code>IdentityUser</code> to extend a standard registration for my MVC 5 site.</p>
  <p>I have my extended <code>UserModel</code>:</p>
  <pre class="lang-cs prettyprint-override"><code>namespace MyMvcSite.Models 
  {
      public class UserModel : IdentityUser 
      {
          public string BillingId { get; set; }
          public virtual ICollection&lt;DatabaseModel&gt; Databases { get; set; }
      }
  }
  </code></pre>
  <p>And my context:</p>
  <pre class="lang-cs prettyprint-override"><code>using MyMvcSite.Models;
  
  namespace MyMvcSite.Web 
  {
      public class AuthContext : IdentityDbContext&lt;UserModel&gt; 
      {
          public AuthContext() : base(&quot;AuthContext&quot;) { }
      }
  }
  </code></pre>
  <p>Now, when I execute the code to register a user:</p>
  <pre class="lang-cs prettyprint-override"><code>public async Task&lt;IdentityResult&gt; RegisterUser(UserModel user) 
  {
      user.Email = user.UserName;
      var result = await _userManager.CreateAsync(user);
      
      return result;
  }
  </code></pre>
  <p>I get this error:</p>
  <blockquote>
  <p>The entity type IdentityUser is not part of the model for the current context.</p>
  </blockquote>
  <p>I can't figure out what this error means, because it looks like I have everything correct. Can anyone tell what might be going wrong???</p>
  <p>I know my connectionString <code>AuthContext</code> is correct because I have used it previously.</p>