Use XPath to query against a user-defined default namespace

This article describes how to use XPath to query against a user-defined default namespace and provides code to reproduce the behavior.

Original product version:   Visual Basic
Original KB number:   288147

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

How To Specify Namespace when Querying the DOM with XPath