public function getCsvString($separator, CsvFile $csv_file = null)
	{
		$csv_file = $csv_file ? $csv_file : $this->csv_file;
		$csv = '';
		if( ! isset($csv_file) )
		{
			throw new NoDataException;
		}
		else
		{
			foreach($csv_file as $key => $csv_line)
			{
				if($key == 0)
				{
					$csv.=$csv_line->getCsvHeader($separator);
				}
				$csv.=$csv_line->getCsvString($separator);
			}
		}

		return $csv;
	}