public function toXMLString()
{
$str = '';
$str .= '<ns:DoDirectPaymentReq>';
if ($this->DoDirectPaymentRequest != null) {
$str .= '<ns:DoDirectPaymentRequest>';
$str .= $this->DoDirectPaymentRequest->toXMLString();
$str .= '</ns:DoDirectPaymentRequest>';
}
$str .= '</ns:DoDirectPaymentReq>';
return $str;
}
