How to specify namespace when querying nodes with XPath?

Question

Short Version

• You do it in .NET with:

  XmlNode.SelectNodes(query, selectionNamespaces);
  

• Can you do it in javascript?

  • https://jsfiddle.net/9ctoxbh0/

• Can you do it in msxml?

Attempt A:

IXMLDOMNode.selectNodes(query); //no namespaces option

Attempt B:

IXMLDOMNode.ownerDocument.setProperty("SelectionNamespaces", selectionNamespaces);
IXMLDOMNode.selectNodes(query); //doesn't work

Attempt C:

IXMLDOMDocument3 doc;
doc.setProperty("SelectionNamespaces", selectionNamespaces);
IXMLDOMNodeList list = doc.selectNodes(...)[0].selectNodes(query); //doesn't work

Long Version

Given an IXMLDOMNode containing a fragment of xml:

<row>
    <cell>a</cell>
    <cell>b</cell>
    <cell>c</cell>
</row>

We can use the IXMLDOMNode.selectNodes method to select child elements:

IXMLDOMNode row = //...xml above

IXMLDOMNodeList cells = row.selectNodes("/row/cell");

and that will return an IXMLDOMNodeList:

• <cell>a</cell>
• <cell>b</cell>
• <cell>c</cell>

And that's fine.

But namespaces break it

If the XML fragment originated from a document with a namespace, e.g.:

<row xmlns:ss="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
    <cell>a</cell>
    <cell>b</cell>
    <cell>c</cell>
</row>

The same XPath query will nothing, because the elements row and cell do not exist; they are in another namespace.

Querying documents with default namespace

If you had a full IXMLDOMDocument, you would use the setProperty method to set a selection namespace:

a b c

You would query the default namespace by giving it a name, e.g.:

• Before: xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"
• After: xmlns:peanut="http://schemas.openxmlformats.org/spreadsheetml/2006/main"

and then you can query it:

IXMLDOMDocument3 doc = //...document xml above
doc.setProperty("SelectionNamespaces", "xmlns:peanut="http://schemas.openxmlformats.org/spreadsheetml/2006/main");

IXMLDOMNodeList cells = doc.selectNodes("/peanut:row/peanut:cell");

and you get your cells:

• <cell>a</cell>
• <cell>b</cell>
• <cell>c</cell>

But that doesn't work for a node

An IXMLDOMNode has a method to perform XPath queries:

selectNodes Method

Applies the specified pattern-matching operation to this node's context and returns the list of matching nodes as IXMLDOMNodeList.

HRESULT selectNodes(  
      BSTR expression,  
      IXMLDOMNodeList **resultList); 

Remarks

For more information about using the selectNodes method with namespaces, see the setProperty Method topic.

But there's no way to specify Selection Namespaces when issuing an XPath query against a DOM Node.

How can I specify a namespace when querying nodes with XPath?

.NET Solution

.NET's XmlNode provides a SelectNodes method that provides accepts a XmlNamespaceManager parameter:

XmlNamespaceManager ns = new XmlNamespaceManager(doc.NameTable);
ns.AddNamespace("peanut", "http://schemas.openxmlformats.org/spreadsheetml/2006/main");
cells = row.SelectNodes("/peanut:row/peanut:cell", ns);

But i'm not in C# (nor am i in Javascript). What's the native msxml6 equivalent?

Edit: Me not so much with the Javascript (jsFiddle)

Complete Minimal Example

program Project3;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils, msxml, ActiveX;

procedure Main;
var
    s: string;
    doc: DOMDocument60;
    rows: IXMLDOMNodeList;
    row: IXMLDOMElement;
    cells: IXMLDOMNodeList;
begin
    s :=
            '<?xml version="1.0" encoding="UTF-16" standalone="yes"?>'+#13#10+
            '<worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">'+#13#10+
            '<row>'+#13#10+
            '    <cell>a</cell>'+#13#10+
            '    <cell>b</cell>'+#13#10+
            '    <cell>c</cell>'+#13#10+
            '</row>'+#13#10+
            '</worksheet>';

    doc := CoDOMDocument60.Create;
    doc.loadXML(s);
    if doc.parseError.errorCode <> 0 then
        raise Exception.CreateFmt('Parse error: %s', [doc.parseError.reason]);

    doc.setProperty('SelectionNamespaces', 'xmlns:ss="http://schemas.openxmlformats.org/spreadsheetml/2006/main"');

    //Query for all the rows
    rows := doc.selectNodes('/ss:worksheet/ss:row');
    if rows.length = 0 then
        raise Exception.Create('Could not find any rows');

    //Do stuff with the first row
    row := rows[0] as IXMLDOMElement;

    //Get the cells in the row
    (row.ownerDocument as IXMLDOMDocument3).setProperty('SelectionNamespaces', 'xmlns:ss="http://schemas.openxmlformats.org/spreadsheetml/2006/main"');
    cells := row.selectNodes('/ss:row/ss:cell');
    if cells.length <> 3 then
        raise Exception.CreateFmt('Did not find 3 cells in the first row (%d)', [cells.length]);
end;

begin
  try
        CoInitialize(nil);
        Main;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

Answer 1

This is answered on MSDN:

How To Specify Namespace when Querying the DOM with XPath

Update:

Note, however, that in your second example XML, the <row> and <cell> elements are NOT in the namespace being queried by the XPath when adding xmlns:peanut to the SelectionNamespaces property. That is why the <cell> elements are not being found.

To put them into the namespace properly, you would have to either:

• change the namespace declaration to use xmlns= instead of xmlns:ss=:

  <row xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
      <cell>a</cell>
      <cell>b</cell>
      <cell>c</cell>
  </row>
  

• use <ss:row> and <ss:cell> instead of <row> and <cell>:

  <ss:row xmlns:ss="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
      <ss:cell>a</cell>
      <ss:cell>b</cell>
      <ss:cell>c</cell>
  </ss:row>
  

The SelectionNamespaces property does not magically put elements into a namespace for you, it only specifies which namespaces are available for the XPath query to use. The XML itself has to put elements into the proper namespaces as needed.

Update:

In your new example, cells := row.selectNodes('/ss:row/ss:cell'); does not work because the XPath query is using an absolute path, where the leading / starts at the document root, and there are no <row> elements at the top of the XML document, only a <worksheet> element. That is why rows := doc.selectNodes('/ss:worksheet/ss:row'); works.

If you want to perform an XPath query that begins at the node being queried, don't use an absolute path, use a relative path instead:

cells := row.selectNodes('ss:row/ss:cell');

Or simply:

cells := row.selectNodes('ss:cell');