public function onBeforeWrite()
    {
        if (!$this->isInDB()) {
            $this->CreatorID = Member::currentUserID();
        }

        if (!$this->VersionNumber) {
            $versions = DataObject::get(
                'FileVersion', sprintf('"FileID" = %d', $this->FileID)
            );

            if ($versions) {
                $this->VersionNumber = $versions->Count() + 1;
            } else {
                $this->VersionNumber = 1;
            }
        }

        if (!$this->Filename) {
            $this->Filename = $this->saveCurrentVersion();
        }

        parent::onBeforeWrite();
    }