Can't load files that has xmlns attribute in the first child with XDocument

Question

I am new to XDocument but I have been looking around for a solution to this problem which I couldn't get to fix.

I need to load some kind of XML files (PNML) that comes this way:

<pnml xmlns="http://www.pnml.org/version-2009/grammar/pnml">
 <net id="id" type ="http://www.pnml.org/version-2009/grammar/ptnet">
  ..........</net> </pnml>

And I couldn't get to load these kind of files unless I add "xmlns" as an Attribute to the node net . Meanwhile, the files I create myself has this xmlns attribute, and I can load them without problems. While, files that are generated from some other software that I need to be able to use from my software doesn't has this "xmlns" attribute, and if I add it myself to the files generated by this software, I can load those files.

Here's the code I am using to Load :

            XDocument doc = XDocument.Load(file);
            XNamespace ns = @"http://www.pnml.org/version-2009/grammar/pnml";

            foreach (XElement element in doc.Element(ns + "pnml")
                                .Elements("net").Elements("page").Elements("place"))
            { // Do my loading to "place" nodes for example }

But whenever I try to load a file, it just skips my "foreach" statement, and if I add some line before "foreach" like:

string id= (string) doc.Element(ns + "pnml")
                                .Element("net").Attribute("id");

it says:

Object reference not set to an instance of an object.

Here's an example of a file generated by my code and also can be read from my code:

<?xml version="1.0" encoding="utf-8"?>
<pnml xmlns="http://www.pnml.org/version-2009/grammar/pnml">
  <net id="netid" type="http://www.pnml.org/version-2009/grammar/ptnet" xmlns="">
    nodes and information </net> </pnml>

NOTE: I use this code to save my files:

            XNamespace ns = @"http://www.pnml.org/version-2009/grammar/pnml";
            XDocument doc = new XDocument
            (
              new XElement(ns+"pnml"
                , new XElement("net",new XAttribute("id", net_id), ...));

I found a way to save my files without this "xmlns" attribute, but once I omit it, I can't load it from my code. And the first example I wrote is the standard format and I really need to get ride of the "xmlns" problem.

EDIT: I'm sorry if you got confused, what I want is to be able to load the standard PNML files that doesn't have thise "xmlns" attribute within the "net" node.

Answer 1

What you're missing is that element namespaces are inherited from their parents .

So your XML:

<pnml xmlns="http://www.pnml.org/version-2009/grammar/pnml">
    <net id="id" type ="http://www.pnml.org/version-2009/grammar/ptnet">
...

Contains two elements. One is pnml with the namespace http://www.pnml.org/version-2009/grammar/pnml , and the child is net which also has the namespace http://www.pnml.org/version-2009/grammar/pnml .

With this in mind, your query on the existing XML should be:

doc.Element(ns + "pnml").Elements(ns + "net")...

And your code to generate the XML should be:

new XElement(ns + "pnml",
    new XElement(ns + "net", new XAttribute("id", net_id), ...));

Answer 2

试试这个

var result = doc.Element(ns + "pnml").Descendants().Where(x=>x.Name.LocalName=="net")