I created a small program that should be able to validate a user's
credentials with the new 3.5 framework.  It seems to work on my laptop
that is joined to a domain, but does not work on my desktop at home
that is in a workgroup.  Does anyone know if that is a limitation?  Is
there something I am doing wrong?
Thanks
Here's the code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.DirectoryServices.AccountManagement;

namespace TryAccount
{
   class Program
   {
       static PrincipalContext m_principalContext;
       static UserPrincipal m_userPrincipal;

       public static bool AuthenticateUser(string username, string
password)
       {
           bool isAuthentic = false;

           try
           {
               if (username.Contains("\\") ||
username.Contains("@"))    //Assuming domain\user for AD, TODO: add
support for user@domain format
               {
                   //string[] holdName = username.Split(new char[]
{ '\\' });
                   m_principalContext = new
PrincipalContext(ContextType.Domain);
                   isAuthentic =
m_principalContext.ValidateCredentials(username, password,
ContextOptions.Negotiate);
               }
               else
               {
                   m_principalContext = new
PrincipalContext(ContextType.Machine);
                   isAuthentic =
m_principalContext.ValidateCredentials(username, password,
ContextOptions.Negotiate);

               }
               if (isAuthentic)
               {
                   m_userPrincipal =
UserPrincipal.FindByIdentity(m_principalContext, username);
                   Console.WriteLine("User " + m_userPrincipal.Name +
" gave a valid password.\n");
                   Console.WriteLine("Last logged on " +
m_userPrincipal.LastLogon + "\n");
                   Console.WriteLine("Last bad password given " +
m_userPrincipal.LastBadPasswordAttempt + "\n");
               }
               return isAuthentic;
           }
           catch (Exception ex)
           {
               Console.WriteLine(ex.ToString() + "\n");
               return isAuthentic;
           }
       }

       static void Main(string[] args)
       {
           string user = "";
           string pass = "";
           bool good = false;
           while (true)
           {
               Console.WriteLine("Please enter a username:");
               user = Console.ReadLine();
               Console.WriteLine("Please enter " + user + "'s
password:");
               pass = Console.ReadLine();
               good = Program.AuthenticateUser(user, pass);
               Console.ReadLine();
           }
       }
   }
}