One of my coworkers was struggling with an XML document with a default namespace, none of his attempts returned any nodes. The main reason for this was that his document contained a default namespace which he didn’t include in the query.

As a reminder here a sample how to query an XML document with a default namespace.

Sample XML document:

<?xml version="1.0" encoding="utf-8" ?>
<root xmlns="urn:paulvanbrenk.com/2008/06">
  <book>
    <author>C. Sells</author>
    <title>Programming WPF</title>
  </book>
  <book>
    <author>C. Petzold</author>
    <title>Application = Code + Markup</title>
  </book>
  <book>
    <author>C. Anderson</author>
    <title>Essential WPF</title>
  </book>
</root> 

This doesn’t work:

// load sample document
XmlDocument doc = new XmlDocument();
doc.Load("../../sample.xml");

// try query without namespace
var node1 = doc.SelectNodes("/root/book/title");

Console.WriteLine("node1.Count == 0 {0}", node1.Count == 0);

If you add an XmlNamespaceManager the call to select nodes is able to resolve the nodes:

// load sample document
XmlDocument doc = new XmlDocument();
doc.Load("../../sample.xml");

// add namespace manager
XmlNamespaceManager xnManager = new XmlNamespaceManager(doc.NameTable);
xnManager.AddNamespace(/* prefix */ "x", /* uri */ @"urn:paulvanbrenk.com/2008/06");

var node2 = doc.SelectNodes("/x:root/x:book/x:title", xnManager);

Console.WriteLine("node2.Count != 0 {0}", node2.Count != 0);

And using XLinq makes it a little more readable:

XDocument xDoc = XDocument.Load("../../sample.xml");
XNamespace x = "urn:paulvanbrenk.com/2008/06";

var node3 = from item
                in xDoc.Elements(x + "root").Elements(x + "book")
            select item.Element(x + "title");

Console.WriteLine("node3.Count() != 0 {0}", node3.Count() != 0);

Note how you query the nodes by combining the XNameSpace and the node name.

sample: sample.zip (2.6 KB)