public function ProfileUrl($UserReference = NULL, $UserID = NULL) {
      if (!property_exists($this, 'User'))
         $this->GetUserInfo();
         
      if ($UserReference === NULL)
         $UserReference = $this->User->Name;
      if ($UserID === NULL)
         $UserID = $this->User->UserID;

      $UserReferenceEnc = rawurlencode($UserReference);
      if ($UserReferenceEnc == $UserReference)
         return $UserReferenceEnc;
      else
         return "$UserID/$UserReferenceEnc";
   }