XML : C# XDocument.XPathEvaluate - Handling namespaces at runtime

I'm trying to display any given xml file in a custom GUI and when the user selects an element or attribute the xpath of that object should be displayed. All the GUI stuff is done, but I am having some issues handling all the namespace stuff at runtime. This is what I have:

  XDocument document = XDocument.Load("somefile.xml");  XPathNavigator navigator = document.CreateNavigator();  navigator.MoveToFollowing(XPathNodeType.Element);  IDictionary<string, string> namespaces = navigator.GetNamespacesInScope(XmlNamespaceScope.All);  XmlReader reader = document.CreateReader();  XmlNamespaceManager manager = new XmlNamespaceManager(reader.NameTable);    foreach (KeyValuePair<string, string> ns in namespaces)      manager.AddNamespace(ns.Key, ns.Value);    

Using XDocument.XPathEvaluate should give me the xpath, but for the given xml it returns 0 matches no matter what xpath i try:

  <?xml version="1.0" encoding="UTF-8"?>  <Invoice xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2" xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2" xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2">      <cbc:UBLVersionID>2.1</cbc:UBLVersionID>      <cbc:IssueDate>2015-06-30</cbc:IssueDate>      ...  </Invoice>    

1) Why is my code unable to produce an xpath for the above xml?

2) Can anyone point me in the right direction on handling "any" given namespace at runtime?