protected function writeDN($dn)
    {
        // prepare DN
        if ($this->_options['encode'] == 'base64') {
            $dn = $this->convertDN($dn).PHP_EOL;
        } elseif ($this->_options['encode'] == 'canonical') {
            $dn = Net_LDAP2_Util::canonical_dn($dn, array('casefold' => 'none')).PHP_EOL;
        } else {
            $dn = $dn.PHP_EOL;
        }
        $this->writeLine($dn, 'Net_LDAP2_LDIF error: unable to write DN of entry '.$this->_entrynum);
    }