How to specify namespace when querying nodes with XPath? - winapi

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');