X-Rechnung CII: missing qdt namespace

Hello,
thank you for the great work on this project, I already use it to read zugferd and plan to use it for x-Rechnung cii and ubl.

I attached an example for X-Rechnung CII 2.0 without the qdt namespace. On InvoiceDescriptor.Load I get a XPathException "namesapce 'qdt' is not defined."

I think it should not be an error, if the namespace is not used in xml.
What is your proposal to handle this error?

INVOICE_cii_200.txt

good point. Currently, only qdt is supported for reading invoices.
It would be pretty easy to write this code more abstract:

ZUGFeRD-csharp/ZUGFeRD/InvoiceDescriptor22CIIReader.cs

Line 377 in 7e6f580

    
           retval.OrderDate = _nodeAsDateTime(doc.DocumentElement, "//ram:ApplicableHeaderTradeAgreement/ram:BuyerOrderReferencedDocument/ram:FormattedIssueDateTime/qdt:DateTimeString", nsmgr);

i.e. create a function which reads the datetime sub node from a given node regardless if it's qdt or udt.

like

retval.OrderDate = _childNodeAsDateTime(doc.DocumentElement, "//ram:ApplicableHeaderTradeAgreement/ram:BuyerOrderReferencedDocument/ram:FormattedIssueDateTime", nsmgr);

DateTime _childNodeAsDateTime(...)
{
// find out if we have a qdt or udt sub node
// apply _nodeAsDateTime() to the respective sub node
}

What do you think?

sounds good. I will create a pull request with the suggested changes.

Thanks, go ahead. I might move this into a separate dedicated class like 'UniversalDataTypeParser' later on though.

I had some spare time and implemented this already. Could you contribute a test case?

Great :), your changes work as expected. Thanks for the quick adjustment. I added tests with #327