How to export all rows as CSV in ModelAdmin (SilverStripe 3.1)?

Apparently the GridFieldExportButton only exports the currently visible data-set (paginated). Is there a way to make it export all the rows from a model?

Or alternatively: Is there a way to show all rows (eg. bypass pagination), so that the user can perform an export after showing all the rows? I don't want to show all rows all the time (which would probably be possible by setting ModelAdmin::set_page_length(<ridiculouslyHighNumber>);) but only on demand.

Solved it by creating a custom subclass of the GridFieldExportButton and using this for my models. The key is to use $gridField->getList(); instead of $gridField->getManipulatedList(); in the generateExportFileData method.

Here's the complete class for anybody interested:

class GridFieldExportAllButton extends GridFieldExportButton {
    /**
     * Generate export fields for CSV.
     *
     * @param GridField $gridField
     * @return array
     */
    public function generateExportFileData($gridField) {
        $separator = $this->csvSeparator;
        $csvColumns = ($this->exportColumns)
            ? $this->exportColumns
            : singleton($gridField->getModelClass())->summaryFields();
        $fileData = '';
        $columnData = array();
        $fieldItems = new ArrayList();

        if($this->csvHasHeader) {
            $headers = array();

            // determine the CSV headers. If a field is callable (e.g. anonymous function) then use the
            // source name as the header instead
            foreach($csvColumns as $columnSource => $columnHeader) {
                $headers[] = (!is_string($columnHeader) && is_callable($columnHeader)) ? $columnSource : $columnHeader;
            }

            $fileData .= "\"" . implode("\"{$separator}\"", array_values($headers)) . "\"";
            $fileData .= "\n";
        }

        $items = $gridField->getList();

        foreach($items as $item) {
            $columnData = array();
            foreach($csvColumns as $columnSource => $columnHeader) {
                if(!is_string($columnHeader) && is_callable($columnHeader)) {
                    if($item->hasMethod($columnSource)) {
                        $relObj = $item->{$columnSource}();
                    } else {
                        $relObj = $item->relObject($columnSource);
                    }

                    $value = $columnHeader($relObj);
                } else {
                    $value = $gridField->getDataFieldValue($item, $columnSource);
                }

                $value = str_replace(array("\r", "\n"), "\n", $value);
                $columnData[] = '"' . str_replace('"', '\"', $value) . '"';
            }
            $fileData .= implode($separator, $columnData);
            $fileData .= "\n";

            $item->destroy();
        }

        return $fileData;
    }
}