Select a XML node based on a sibling node

Question

I'm trying to select an XML node, where another child of the parent node contains a specific value.

The XML looks like this:

<?xml version="1.0" encoding="UTF-8" ?>
<AuthorIT>
    <Objects>
        <Media>don't care</Media>
        <Style>don't care</Style>
        <Book>don't care</Book>
        <Topic>don't care</Topic>
        <Topic>
            <Object>
                <Description>Performance Evidence</Description>
            </Object>
            <Text>This is what I want to select</Text>
        </Topic>
    </Objects>
</AuthorIT>

I'm using XPath in C#. My query at the moment looks like this: (but doesn't work, obviously)

docNav = new XPathDocument(localFile);
nav = docNav.CreateNavigator();
xPath = "//Topic[Object/Description = 'Performance Evidence']/Text";
string value = nav.SelectSingleNode(xPath).Value;

How do I get the contents of the Text node, from the Topic that has an Object/Description value of "Performance Evidence"?

Your XPath is correct. Can you specify what exactly is not working? — Kirill Polishchuk
– Kirill Polishchuk, Commented Sep 27, 2019 at 1:07
@KirillPolishchuk nav.SelectSingleNode(xPath) is returning null. If I have the XPath correct, am I doing something wrong with the rest of the c#? — Adeptus
– Adeptus, Commented Sep 27, 2019 at 1:32
So... I've been trying to get the data through other methods. I can traverse the tree using an XmlDocument and foreach(XmlNode node in xmlNodeList), but not through xmlDocument.SelectSingleNode(...). I'd rather not have 5+ nested foreach loops just to find the node I want... Any suggestions, or should I make this a new question? — Adeptus
– Adeptus, Commented Sep 27, 2019 at 5:08

Richard Woods · Accepted Answer · 2019-09-27 01:05:58Z

1

You should first select the Description node containing your needle text, then move back to the common parent and select the Text nodes that are its children.

//Topic/Object/Description[text()='Performance Evidence']/../../Text/text()

answered Sep 27, 2019 at 1:05

Richard Woods

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Adeptus · Accepted Answer · 2019-09-30 06:51:03Z

0

As Kirill Polishchuk said in a comment, my XPath was correct.

What I left out of the example XML was the key to the solution... Namespace!

I found my answer on this other question: Using Xpath With Default Namespace in C#

answered Sep 30, 2019 at 6:51

Adeptus

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