title: AD LDS ValidateCredentials at ContextType.ApplicationDirectory can't authenticate
body: <p>I'm trying to use AD LDS for user authentication in my MVC app. I've managed to write some code that allows me to create/edit/delete users and groups, but i can't seem to authenticate them. Here is my sample code:</p>
  
  <pre class="lang-cs prettyprint-override"><code>using( var context = new PrincipalContext(ContextType.ApplicationDirectory, "Lenovo_T61-LapT",
                                      "CN=Kontrahenci,DC=TestApp,DC=local"))
  {
      var userName = "avg.joe";
      var email = "avg.joe@smwhr.us";
      var password = "123456";
      var user = new UserPrincipal(context)
      {
          Name = userName,
          EmailAddress = email
      };
      user.SetPassword(password);
      user.Save();
      if (context.ValidateCredentials(userName , password, ContextOptions.SimpleBind))
          Console.WriteLine("Hooray!");
  
      user.Dispose();
  }
  </code></pre>
  
  <p>Unfortunately this never gets to "Writeline" giving only an error that either the password or username are incorrect.</p>
  
  <p>I've played around with ContextOptions but without any luck.</p>
  
  <p>Any ideas?</p>