XPath search problem

["Marshall, Steven (SKM)" <SMarshall@skm.com.au>]

I'm having a problem getting a .NET XMLDocument to give me back the set
of nodes I want.  The relevant code looks like this:
 
Dim nl as XMLNodelist
Dim nsm as XMLNamespaceManager
 
nl=xDoc.SelectNodes("//codelistItem/CodeListDictionary[@gml:id='Language
Code']/codeEntry", nsm)
 
I have created the NamespaceManager and added to it every namespace
mentioned in the XML document.  The SelectNodes always returns an empty
nodelist, unless I reduce it to a trivial Xpath expression like "//*",
which is not much use.  If I use this exact same Xpath expression in
Altova XMLSpy, it works perfectly and gives me the exact set of nodes I
want.  I'm almost sure that it is the multiple namespaces that are
somehow getting in the way here, but I can't see what's happening.  Here
is the first part of the XML document - sorry about the formatting.
There definitely is a <CodeListDictionary> element further down that has
a gml:id='LanguageCode'.  Anyone know what's happening here?
 


<?xml version="1.0" encoding="UTF-8"?>
<CT_CodelistCatalogue xmlns="http://www.isotc211.org/2005/gmx";
  xmlns:gco="http://www.isotc211.org/2005/gco";
xmlns:gml="http://www.opengis.net/gml";
  xmlns:xlink="http://www.w3.org/1999/xlink";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
  xsi:schemaLocation="http://www.isotc211.org/2005/gmx ../gmx/gmx.xsd
http://www.isotc211.org/2005/gco ../gco/gco.xsd
http://www.opengis.net/gml ../gml/gml.xsd http://www.w3.org/1999/xlink
../xlink/xlinks.xsd">

<!--=====Catalogue description=====-->
  <name>
    <gco:CharacterString>ADO_Codelists</gco:CharacterString>
  </name>
  <scope>
    <gco:CharacterString>Codelists for description of metadata datasets
compliant with ADO_DM_MDP Version 1.0.2</gco:CharacterString>
  </scope>
  <fieldOfApplication>
    <gco:CharacterString>GMX (and imported)
namespace</gco:CharacterString>
  </fieldOfApplication>
  <versionNumber>
    <gco:CharacterString>0.1</gco:CharacterString>
  </versionNumber>
  <versionDate>
    <gco:Date>2007-03-01</gco:Date>
  </versionDate>

<!--============================= Codelists
=======================================-->
<!--=== DP_DateTypeCode ===-->

  <codelistItem>
  <CodeListDictionary gml:id="DP_DateTypeCode">
    <gml:description>identification of when a given event
occurred</gml:description>
    <gml:identifier
codeSpace="ISOTC211/19115">DP_DateTypeCode</gml:identifier>
    <codeEntry>
      <CodeDefinition gml:id="DP_DateTypeCode_creation">
        <gml:description>date identifies when the resource was brought
into existence</gml:description>
        <gml:identifier codeSpace="ADO_DM_MDP">creation</gml:identifier>
      </CodeDefinition>
    </codeEntry>

    <codeEntry>
      <CodeDefinition gml:id="DP_DateTypeCode_publication">
        <gml:description>date identifies when the resource was
issued</gml:description>
        <gml:identifier
codeSpace="ADO_DM_MDP">publication</gml:identifier>
      </CodeDefinition>
    </codeEntry>

    <codeEntry>
      <CodeDefinition gml:id="DP_DateTypeCode_revision">
        <gml:description>date identifies when the resource was examined
or re-examined and imporved or amended</gml:description>
        <gml:identifier codeSpace="ADO_DM_MDP">revision</gml:identifier>
      </CodeDefinition>

 
.....and so on

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