AD LDS ValidateCredentials at ContextType.ApplicationDirectory can't authenticate

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:

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.Validate开发者_JS百科Credentials(userName , password, ContextOptions.SimpleBind))
        Console.WriteLine("Hooray!");

    user.Dispose();
}

Unfortunately this never gets to "Writeline" giving only an error that either the password or username are incorrect.

I've played around with ContextOptions but without any luck.

Any ideas?

---

So I've found the solution which I posted on a similar question.

What I did, and works for me, is when calling ValidateCredentials I modified the username a bit:

bool auth = context.ValidateCredentials(
                            String.Format("CN={0},CN=Kontrahenci,DC=TestApp,DC=loc",
                                          userName), 
                            password);

Hope this helps.