List<string> GetWindowsGroupsUsingAD(string contextType)
        {
            var result = new List<string>();
            try
            {
                // set up domain context
                UserPrincipal = null;
                PrincipalContext context = new PrincipalContext((ContextType)Enum.Parse(typeof(ContextType), contextType));
                string name = WebUserName;
                if (WebPrincipal != null) name = WebPrincipal.Identity.Name;
                if (Identity != null) name = Identity.Name;

                var user = new UserPrincipal(context);
                user.SamAccountName = name;
                var searcher = new PrincipalSearcher(user);
                user = searcher.FindOne() as UserPrincipal;
                if (user == null) user = UserPrincipal.FindByIdentity(context, name);

                if (user != null)
                {
                    UserPrincipal = user;
                    var groups = user.GetAuthorizationGroups();
                    // enumerate over them
                    foreach (Principal p in groups)
                    {
                        result.Add(p.Name);
                    }
                }
                else throw new Exception("Unable to find user:" + name);
            }
            catch (Exception ex)
            {
                if (_tryAgainAD)
                {
                    _tryAgainAD = false;
                    result = GetWindowsGroupsUsingAD(contextType);
                }
                else
                {
                    Warning += "Error getting groups using AD...\r\n" + ex.Message + "\r\n";
                }
            }
            return result;
        }