How to use XPath on TXMLDocument which has namespace prefixes?

Question

I have an XML packet received from a third-party web server:

Answer 1

When I tried this a couple of years ago, I found namespace lookup in XPath was different between xml providers.

If I remember correctly, the Msxml lets you just use the namespace prefixes as they are defined in the xml file.

The ADOM 4 provider requires that you resolve namespace prefixes used in your XPath query to the actual namespaces, independent of the namespace mapping used in the xml file. There is a method pointer for that purpose, OnOx4XPathLookupNamespaceURI. Then you can have a name lookup function like this:

procedure TTestXmlUtil.EventLookupNamespaceURI(
  const AContextNode: IDomNode; const APrefix: WideString;
  var ANamespaceURI: WideString);
begin
  if APrefix = 'soap' then
    ANamespaceURI := 'http://schemas.xmlsoap.org/soap/envelope/'
  else if APrefix = 'some' then
    ANamespaceURI := 'http://someurl'
end;

Using this lookup function, and the selectNode function (which looks like something I may have once posted in a Delphi forum, taken from https://github.com/Midiar/adomxmldom/blob/master/xmldocxpath.pas), I could do the following test (using your xml in a string constant):

procedure TTestXmlUtil.SetUp;
begin
  inherited;
  DefaultDOMVendor := sAdom4XmlVendor;
  docFull := LoadXmlData(csSoapXml);

  OnOx4XPathLookupNamespaceURI := EventLookupNamespaceURI;
end;

procedure TTestXmlUtil.Test_selectNode;
var
  xn: IXmlNode;
begin
  xn := selectNode(docFull.DocumentElement, '/soap:Envelope/soap:Body/some:SomeResponse/some:SomeResult');
  CheckNotNull(xn, 'selectNode returned nil');
end;

I had to modify you XPath query a little for the default namespace.