域登录验证

        public bool TryAuthenticate(string domain, string userName, string password)
        {
            bool isLogin = false;
            try
            {
                DirectoryEntry entry = new DirectoryEntry(string.Format("LDAP://{0}", domain), userName, password);
                entry.RefreshCache();
                isLogin = true;
            }
            catch
            {
                isLogin = false;
            }
            return isLogin;
        }