I have the following example XML file:

<Top xmlns="abbr:SomeNSValue">
  <Next>
    <Other>SomeValue</Other>
  </Next>
</Top>

I load it up and try to read it like this:

FileStream stream = new FileStream(@".\TestXML.xml", FileMode.Open);
XPathDocument xPathDocument = new XPathDocument(stream);
XPathNavigator navigator = xPathDocument.CreateNavigator();

XmlNamespaceManager ns = null;
if (navigator.NameTable != null)
{
    ns = new XmlNamespaceManager(navigator.NameTable);
    ns.AddNamespace("abbr", "SomeNSValue");
}

XPathNodeIterator iterator = navigator.Select("/Top/Next", ns);
iterator.MoveNext();

Console.WriteLine(iterator.Current.InnerXml);

This outputs the Full XML shown above. Not what I am looking for (I want to select the contents of the "Next" node.

But if I take the xmlns="abbr:SomeNSValue out of the XML and try again then I get what I was looking for:

<Other>SomeValue</Other>

In my real scenario I have the XML fed to me and I would rather not have to modify it to take the Namespace off.

Is there a way I can make this work with the namespace in it?

Note: Incase it matters this is the actual namespace that I have in my XML file: xmlns="urn:hl7-org:v2xml"

Your namespace declaration is wrong:

<Top xmlns:abbr="SomeNSValue">
  <Next>
    <Other>SomeValue</Other>
  </Next>
</Top>

When you do this magical change the rest of your code works :)..