public function GetOrderByString($sDirection = null)
    {
        if (is_null($sDirection)) {
            $sDirection = $this->fieldOrderDirection;
        }
        $sOrderBy = '';
        if (!empty($this->fieldSqlOrderBy)) {
            $sOrderBy = $this->fieldSqlOrderBy.' '.$sDirection;
        }

        if (!empty($this->fieldSqlSecondaryOrderByString)) {
            $sOrderBy .= ', '.$this->fieldSqlSecondaryOrderByString;
        }

        return $sOrderBy;
    }