protected void Button1_Click1(object sender, EventArgs e)
        {

            string dominName = "ldap://domain.com:121";
            string userName = "guest";
            string password = "testlogin";

            if (true == AuthenticateUser(dominName, userName, password))
            {
                Response.Redirect("default.aspx");
            }
            else
            {
                Response.Write("Invalid user name or Password!");
            }

        }

        public bool AuthenticateUser(string domain, string username, string password)
        {
            DirectoryEntry entry = new DirectoryEntry(domain, username, password);
            try
            {
                DirectorySearcher search = new DirectorySearcher(entry);
                search.Filter = "(sAMAccountName=" + username + ")";
                search.PropertiesToLoad.Add("cn");
                Response.Write(domain);
                SearchResult result = search.FindOne();

                if (null == result)
                {
                    return false;
                }

            }
            catch (Exception ex)
            {
                return false;
                throw new Exception("Error authenticating user." + ex.Message);
            }
            return true;
        }