title: Active Directory PrincipalContext.ValidateCredentials domain disambiguation
body: <p>I'm dealing with two domains - one is a trusted domain.  There may be a JohnSmith on one domain and another JohnSmith on the other.  Both of these people need to log into my application.</p>
  
  <p>My problem: it doesn't matter which domain I pass in - this code returns true! <strong>How do I know which JohnSmith is logging in?</strong></p>
  
  <pre><code>    static public bool CheckCredentials(
          string userName, string password, string domain)
      {
          using (var context = new PrincipalContext(ContextType.Domain, domain))
          {
              return context.ValidateCredentials(userName, password);
          }
      }
  </code></pre>