public function isValid(&$msg = null)
    {
        try {
            $this->_validateProperties($this->_properties);
        } catch (\Exception $exc) {
            $msg = $exc->getMessage();
            return false;
        }

        if (is_null($this->getPartitionKey())
            || is_null($this->getRowKey())
        ) {
            $msg = Resources::NULL_TABLE_KEY_MSG;
            return false;
        } else {
            return true;
        }
    }