I've got an Xml document that both defines and references some namespaces. I load it into an XmlDocument object and to the best of my knowledge I create a XmlNamespaceManager object with which to query Xpath against. Problem is I'm getting XPath exceptions that the namespace "my" is not defined. How do I get the namespace manager to see that the namespaces I am referencing are already defined. Or rather how do I get the namespace definitions from the document to the namespace manager.

Furthermore tt strikes me as strange that you have to provide a namespace manager to the document which you create from the documents nametable in the first place. Even if you need to hardcode manual namespaces why can't you add them directly to the document. Why do you always have to pass this namespace manager with every single query? What can't XmlDocument just know?

The Code:

XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(programFiles + @"Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\FEATURES\HfscBookingWorkflow\template.xml");
            XmlNamespaceManager ns = new XmlNamespaceManager(xmlDoc.NameTable);

            XmlNode referenceNode = xmlDoc.SelectSingleNode("/my:myFields/my:ReferenceNumber", ns);
            referenceNode.InnerXml = this.bookingData.ReferenceNumber;

            XmlNode titleNode = xmlDoc.SelectSingleNode("/my:myFields/my:Title", ns);
            titleNode.InnerXml = this.bookingData.FamilyName;

...

The Xml:

  <?xml version="1.0" encoding="UTF-8" ?> 
  <?mso-infoPathSolution name="urn:schemas-microsoft-com:office:infopath:Inspection:-myXSD-2010-01-15T18-21-55" solutionVersion="1.0.0.104" productVersion="12.0.0" PIVersion="1.0.0.0" ?> 
  <?mso-application progid="InfoPath.Document" versionProgid="InfoPath.Document.2"?> 
- <my:myFields xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:my="http://schemas.microsoft.com/office/infopath/2003/myXSD/2010-01-15T18:21:55" xmlns:xd="http://schemas.microsoft.com/office/infopath/2003">
  <my:DateRequested xsi:nil="true" /> 
  <my:DateVisited xsi:nil="true" /> 
  <my:ReferenceNumber /> 
  <my:FireCall>false</my:FireCall> 

...