Using XPATH to access XML elements (was: Good tutorial to learn xpath)

c# xml xpath

22,811

Solution 1

Maybe the XML is not the one you posted but has a default namespace declaration. That is the main reason why XPath expressions written by beginners don't select what they want to select. You would need an XmlNamespaceManager http://msdn.microsoft.com/en-us/library/6k4x060d.aspx in that case.

Solution 2

I'd go for the classic W3Schools tutorial. That's how I learnt, and it did me fine. Definitely covers all the basics.

Solution 3

MSDN XPath syntax

Solution 4

I found that the tutorials on zvon are quite good.

Here is the XPath tutorial.

Solution 5

http://www.w3schools.com/xsl/xpath_intro.asp

There is a tutorial in the top and also xpath reference.

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22,811

Author by

Sylverdrag

Updated on August 11, 2020

Comments

Sylverdrag almost 4 years

I am trying to learn XPath. The theory seems extremely simple, except for the fact that it doesn't work.

I am trying to get the content of every target element

XPathDocument doc = new XPathDocument(sPath);
XPathNavigator nav = doc.CreateNavigator();
XPathExpression expr;
expr = nav.Compile("/doc/file/body/trans-unit/target");
XPathNodeIterator iterator = nav.Select(expr);

while (iterator.MoveNext())
{
    XPathNavigator nav2 = iterator.Current.Clone();
    sbDoc.Append(nav2.InnerXml);
}

The XML doc looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<doc version="1.2">
  <file original="affiliate.php" source-language="EN-US" target-language="FR-FR" datatype="php">
    <header>
      <skl>
        <external-file href="affiliate.php"/>
      </skl>
    </header>
    <body>
      <trans-unit id="tu1">
        <source xml:lang="EN-US">Your Program Details</source>
        <target xml:lang="FR-FR">Your Program Details</target>
      </trans-unit>
      <trans-unit id="tu2">
        <source xml:lang="EN-US">Status</source>
        <target xml:lang="FR-FR">Status</target>
      </trans-unit>

This is nearly word for word from a tutorial, but I can't get it to work. When the iterator is created, in debug mode, I can see that the document is loaded, but iterator finds no result and skips the While loop.

I am probably doing something extremely stupid, but what?

Anyone knows where I can find a good, reliable XPATH tutorial?

Thanks all. Turns out I ignored the fact that there was a namespace (which I removed while simplifying the XML code as I didn't realize it was important), and with the addition of a namespace manager, the code works fine.

I am now studying the XPATH tutorials proposed and they look good.

Admin almost 14 years

Ja! Ja! We always see answers to technical questions about javascript (and even about CSS) recommending to use a library like JQuery. But I've never seen it recommended as the tutorial!
Sylverdrag almost 14 years

Thanks Martin. You are right, there was a namespace on the original which I removed when "simplifying" the XML file, and of course, now it works.
Sylverdrag almost 14 years

Looks like a great tutorial. Thanks!
Admin almost 14 years

@Sylverdrag: And how this answer serves your question title "Good tutorial to learn xpath". I think you should edit that.
Sylverdrag almost 14 years

@Alejandro: It was a 2-in-1 question, and I kind of have to hand it over to the person who manages to spot the underlying problem, although I did upvote the good tutorial answers.