Use XPath to find a node by name attribute value

Question

I am trying to find a node by the name attribute value.

Here is a sample of the xml document:

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE kfx:XMLRELEASE SYSTEM "K000A004.dtd">
<kfx:XMLRELEASE xmlns:kfx="http://www.kofax.com/dtd/">
  <kfx:KOFAXXML>
    <kfx:BATCHCLASS ID="00000008" NAME="CertficateOfLiability">
      <kfx:DOCUMENTS>
        <kfx:DOCUMENT DOCID="00000006" DOCUMENTCLASSNAME="COL">
          <kfx:DOCUMENTDATA>
            <kfx:DOCUMENTFIELD NAME="Producer Name" VALUE="Howalt+McDowell Insurance" />
           ...
           ....

Here is my attempted expression:

 var xml = XDocument.Load(new StreamReader("C:\\Users\\Matthew_cox\\Documents\\test.xml"));
 XNamespace ns = "http://www.kofax.com/dtd/";
 XmlNamespaceManager nsm = new XmlNamespaceManager(xml.CreateNavigator().NameTable);
 nsm.AddNamespace("kfx", ns.NamespaceName);

 var docs = xml.Descendants(ns + "DOCUMENT");
 foreach(var doc in docs)
 {
      doc.XPathSelectElement("/DOCUMENTDATA/DOCUMENTFIELD/[@name='Producer Name']", nsm); //this line produces this exception: Expression must evaluate to a node-set.
 }

Kirill Polishchuk · Accepted Answer · 2011-11-15 17:56:38Z

1

XML is case-sensitive. In provided XML kfx:DOCUMENTFIELD has NAME attribute. Also your XPath doesn't have reference to namespace.

Try this XPath:

kfx:DOCUMENTDATA/kfx:DOCUMENTFIELD[@NAME = 'Producer Name']

edited Nov 15, 2011 at 17:56

answered Nov 15, 2011 at 17:21

Kirill Polishchuk

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6 Comments

Matthew Cox Over a year ago

I did provide a XmlNamespaceManger object as you will note above. I assumed that would handle the namespacing part but apparrantly not. However, even with your version my compiler still throws the same exception as if I am not producing an expression intended to return a result set or something.

Tony Hopkinson Over a year ago

It does if you include teh prefix in the Xpath as in. SelectNode("kfx:SomeNodeName/kfx:SomeChildName",SomeNameSpaceManager)

Matthew Cox Over a year ago

@Kirill Polishchuk I stripped out of the namespaces to simplify the learning curve (if you haven't noticed this is my very first time with XML or XPath for that matter). I can get the item I'm after if I construct my query like so:

doc.XPathSelectElements("XMLRELEASE/KOFAXXML/BATCHCLASS/DOCUMENTS/DOCUMENT/DOCUMENTDATA/DOCUMENTFIELD[@NAME='Producer Name']")

There has got to be a better way though, have to start from the root and work my way all the way down is ridiculous.

Kirill Polishchuk Over a year ago

@MatthewCox, Try this one: //DOCUMENTFIELD[@NAME='Producer Name']

Matthew Cox Over a year ago

@Kirill Polishchuk That is a much cleaner approach. I must apoligize. My actual code is much different than the exmaple I posted, trying to condense it to make the problem easier to identify. However, I mostly coded the example code in the question from scratch and I just noticed that my actual code was performing my searches from the original XML root node ... no wonder many of these attempts where failing. The help was much appreciated

|

Matthew Cox · Accepted Answer · 2011-11-15 17:40:56Z

1

I see two things wrong.

First of all you are selecting starting with "/", this selects from the document root, so strip the leading slash.

Secondly the expression is a bit wierd. I would include the condition directly on DOCUMENTFIELD. (I am unsure if no expression on the node axis actually means something. As in is .../[..] equivalent to .../node()[..] or perhaps even .../*[..]?)

As Kirill notes, you should also watch the casing and namespaces, but this should solve c# complaining about expressions not evaluating to node sets:

kfx:DOCUMENTDATA/kfx:DOCUMENTFIELD[@NAME = 'Producer Name']

edited Nov 15, 2011 at 17:40

Matthew Cox

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answered Nov 15, 2011 at 17:29

Captain Coder

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2 Comments

Matthew Cox Over a year ago

A step in the right direction (no more exception). However, apparently my query is incorrect as it produces no results. Any thoughts on the issue?

Captain Coder Over a year ago

I personally never bother with the namespace manager. Have you tried removing it? Ohh just noticed I made a typeo btw... first namespace should be kfx not kxf, perhaps that is it. If that doesn't work strip all namespaces everywhere (source, ns-manager and query) and add them back in in steps. That eventually fixes it for me.

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