XmlElement.SelectNodes(..) - finds nothing.. Help?

Question

Sorry to bother you with such a simple question, but I'm stuck here since an hour:

I have an xml file that looks something like this:

<?xml version="1.0" encoding="utf-8"?>
<aaa xmlns="http://blabla.com/xmlschema/v1">

  <bbb>
    <ccc>Foo</ccc>
  </bbb>

  <ddd x="y" />
  <ddd x="xx" />
  <ddd x="z" />

</aaa>

I'm trying to access the elements 'ddd' like this:

var doc = new XmlDocument();
doc.Load("example.xml");
foreach (XmlNode dddNode in doc.DocumentElement.SelectNodes("//ddd"))
{
   // do something
   Console.WriteLine(dddNode.Attributes["x"].Value);
}

At runtime the foreach loop is skipped because I don't get any nodes back from the .SelectNodes method. I breaked before the loop and had a look at the InnerXML, that looks fine, and I also tried all sorts of XPaths (like "//bbb" or "/aaa/ddd"), but only "/" seems to not return null.

This exact code worked for me before, now it does not. I suspect something with that namespace declaration in the aaa tag, but I couldn't figure out why this should cause problems. Or.. can you see anything I may be missing?

Answer 1

This is xml-namespaces. There is no ddd. There is, however, x:ddd where x is your alias to http://blabla.com/xmlschema/v1. You'll need to test with namespaces - for example:

var nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("x", "http://blabla.com/xmlschema/v1");
var nodes = doc.DocumentElement.SelectNodes("//x:ddd", nsmgr);
// nodes has 3 nodes

Note x in the above is arbitrary; there is no significance in x other than convenience.

This (rather inconveniently) means adding the namespace (or an alias, as above) into all of your xpath expressions.