XPATHS and Default Namespaces

Question

What is the story behind XPath and support for namespaces? Did XPath as a specification precede namespaces? If I have a document where elements have been given a default namespace:

<foo xmlns="uri" />

It appears as though some of the XPath processor libraries won't recognize //foo because of the namespace whereas others will. The option my team has thought about is to add a namespace prefix using regular expressions to the XPath (you can add a namespace prefix via XmlNameTable) but this seems brittle since XPath is such a flexible language when it comes to node tests.

Is there a standard that applies to this?

My approach is a bit hackish but it seems to work fine; I remove the xmlns declaration with a search/replace and then apply XPath.

string readyForXpath = Regex.Replace(xmldocument, "xmlns=\".+\"", String.Empty );

Is that a fair approach or has anyone solved this differently?

Answer 1

You need local-name():

http://www.w3.org/TR/xpath#function-local-name

To crib from http://web.archive.org/web/20100810142303/http://jcooney.net:80/archive/2005/08/09/6517.aspx:

<foo xmlns='urn:foo'>
  <bar>
    <asdf/>
  </bar>            
</foo>

This expression will match the “bar” element:

  //*[local-name()='bar'] 

This one won't:

 //bar

Answer 2

I tried something similar to what palehorse proposed and could not get it to work. Since I was getting data from a published service I couldn't change the xml. I ended up using XmlDocument and XmlNamespaceManager like so:

XmlDocument doc = new XmlDocument();
doc.LoadXml(xmlWithBogusNamespace);            
XmlNamespaceManager nSpace = new XmlNamespaceManager(doc.NameTable);
nSpace.AddNamespace("myNs", "http://theirUri");

XmlNodeList nodes = doc.SelectNodes("//myNs:NodesIWant",nSpace);
//etc