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Finding elements with XPath in Delphi

Answer 1

A:

Any possibility you need to escape the / ?

Toby Allen 2009-09-10 18:26:42

No, it is Delphi.

Lars Truijens 2009-09-10 19:42:54

Answer 2

+1 A:

In the example code I find online for the selectNodes method, it is preceded by code that sets the document's SelectionNamespaces property via setProperty. Some even set SelectionLanguage, too.

Doc.setProperty('SelectionLanguage', 'XPath');
Doc.setProperty('SelectionNamespaces',
  'xmlns:xsl=''http://www.w3.org/1999/XSL/Transform''');

Based on the element names you're searching for, I guess you're processing an HTML file. The basic HTML elements are in the http://www.w3.org/1999/xhtml namespace, so try this:

Doc.setProperty('SelectionNamespaces',
  'xmlns:x=''http://www.w3.org/1999/xhtml''');
List := Doc.selectNodes('/x:html/x:head');

See also:

selectNodes does not give node list when xmlns is used on Microsoft's forum.

Rob Kennedy 2009-09-10 18:32:38

I don't think it is the reason here. Moreover setProperty only exists in IXMLDOMDocument2, not in IXMLDOMDocument.

François 2009-09-10 20:26:41

Answer 3

+1 A:

IXMLDOMDocument.Load() does not raise an exception if something goes wrong with you file or with its content. Try the following to be sure there is nothing bad with it :

...
Doc.load(Filename);
if Doc.parseError.errorCode <> 0 then
  ShowMessage('Error : ' + + Doc.parseError.reason) 
else
  ShowMessage('No problem so far !');
...

I suck at XPath but mabe if html is your root node you don't need to include it in your query string, so try the following :

List:=Doc.selectNodes('//html/head');

or

List:=Doc.selectNodes('//head');

Fred 2009-09-10 19:06:07

Answer 4

+2 A:

If you're just trying to load a plain html file as xml, it would probably have multiple reasons to fail and choke on things like:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"&gt;

You have to test that it actually loads correctly before doing anything else:

  if not Doc.load(filename) then
    raise Exception.Create('XML Loading error:' + Trim(Doc.parseError.reason));

It will give you the specific reason for the failure like this one:

XML Loading error:End tag 'head' does not match the start tag 'link'.

François 2009-09-10 20:14:19

This was very helpful for me, parseError caught an ID10T error on my part.

Chris Miller 2010-03-23 20:24:44

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Finding elements with XPath in Delphi

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