public static function getList()
    {
        $db = Database::connection();
        $handles = $db->GetCol('select cnvRatingTypeHandle from ConversationRatingTypes order by cnvRatingTypeHandle asc');
        $types = array();
        foreach ($handles as $handle) {
            $ratingType = static::getByHandle($handle);
            if (is_object($ratingType)) {
                $types[] = $ratingType;
            }
        }

        return $types;
    }