How to use XPath to query against a user-defined default namespace

Symptoms

When you redefine the default namespace in the XML document, change the internal SelectionNamespaces property for the default namespace, and then try to programmatically use XPath to return nodes by using the selectNodes or selectSingleNodes method, no nodes are returned.

Resolution

Either use prefixes with the namespaces when you specify the SelectionNamespaces property, or use Extensible Stylesheet Language (XSL) pattern-matching operations instead of XPath.

More Information

This behavior is by design.

Implementation of XPath queries against the DOMDocument requires that namespaces be declared in the Document Object Model (DOM) before the selectNodes or selectSingleNode methods are run.

Steps to reproduce the behavior

  1. In Visual Basic, create a new Standard EXE project. Form1 is created by default.
  2. Paste the following code into the Form_Unload() event of Form1.
        
    ' You can change the ProgID to reflect the installed version of the Microsoft XML Parser:
    ' For example, with MSXML 6, you would use:
    ' Dim xmlDom As MSXML2.DOMDocument60
    Dim xmlDom As MSXML2.DOMDocument
    Dim nodeList As MSXML2.IXMLDOMNodeList
    Dim iNode As MSXML2.IXMLDOMNode

    ' For example, with MSXML 6, you would use:
    ' Set xmlDom = New MSXML2.DOMDocument60

    Set xmlDom = New MSXML2.DOMDocument

    With xmlDom
    .async = False
    .loadXML "<?xml version='1.0'?>" & _
    "<Root xmlns='uri:MyNameSpace'>" & _
    " <Test>This is a Test</Test>" & _
    "</Root>"
    .setProperty "SelectionLanguage", "XPath"
    .setProperty "SelectionNamespaces", "xmlns='uri:MyNameSpace'"
    Set nodeList = .selectNodes("//Test")
    End With

    For Each iNode In nodeList
    msgbox iNode.xml
    Next iNode
  3. On the Project menu, click References. From the list of available references, select Microsoft XML,v3.0 or later.
  4. Run the project. No XML is returned.
  5. Comment out the two setProperty methods.NOTE: Alternatively, you can modify the two lines of code as follows.
            .setProperty "SelectionNamespaces", "xmlns:myNS='uri:MyNameSpace'"
    Set nodeList = .selectNodes("//myNS:Test")
  6. Run the project. The XML nodes are returned.

REFERENCES

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

294797 How To Specify Namespace when Querying the DOM with XPath

Eigenschaften

Artikelnummer: 288147 – Letzte Überarbeitung: 22.06.2014 – Revision: 1

Feedback