XPath: select a node based on another node?

Question

Consider the following XML:

<Items>
    <Item>
        <Code>Test</Code>
        <Value>Test</Value>
    </Item>
    <Item>
        <Code>MyCode</Code>
        <Value>MyValue</Value>
    </Item>
    <Item>
        <Code>AnotherItem</Code>
        <Value>Another value</Value>
    </Item>
</Items>

I would like to select the Value node of the Item that has the Code node in with the value MyCode. How would I go about using XPath?

I've tried using Items/Item[Code=MyCode]/Value but it doesn't seem to work.

Try setting MyCode in astring like this "MyCode", and if it is possible I would recommend using [Linq-to-XML](http://msdn.microsoft.com/en-us/library/bb387098.aspx). — Yet Another Geek, Jun 01 '11 at 15:29
@alexbrn: The bad XML may well be part of the problem, so should be in the answer (in this case). I've addressed it in my answer, for example. I suggest leaving the question how it was asked. — Merlyn Morgan-Graham, Jun 01 '11 at 15:36
Changed the XML. My XML is a little bit more complex :P. Was just a typo. — Kees C. Bakker, Jun 01 '11 at 15:37
Sorry about that. Please edit again, and I won't "fix" the changes :) Make sure you take care of the `Value` end tags too - right now they're `Code` end tags. — Merlyn Morgan-Graham, Jun 01 '11 at 15:39

score 7 · Accepted Answer · answered Jun 01 '11 at 15:32

Your XML data is wrong. The Value tag doesn't have correct matching closing tags, and your Item tags don't have matching closing tags (</Item>).

As for your XPath, try enclosing the data you want to match in quotes:

const string xmlString =
@"<Items>
    <Item>
        <Code>Test</Code>
        <Value>Test</Value>
    </Item>
    <Item>
        <Code>MyCode</Code>
        <Value>MyValue</Value>
    </Item>
    <Item>
        <Code>AnotherItem</Code>
        <Value>Another value</Value>
    </Item>
</Items>";

var doc = new XmlDocument();
doc.LoadXml(xmlString);
XmlElement element = (XmlElement)doc.SelectSingleNode("Items/Item[Code='MyCode']/Value");
Console.WriteLine(element.InnerText);

Yes, without the quotes it tries to compare the value of the node Code, to the value of the node MyCode. As expected it doesn't find a node called MyCode. — Chris Chilvers, Jun 03 '11 at 09:52

score 1 · Answer 2 · answered Jun 01 '11 at 15:37

You need:

/Items/Item[Code="MyCode"]/Value

Assuming you fix-up your XML:

<?xml version="1.0"?>
<Items>
  <Item>
    <Code>Test</Code>
    <Value>Test</Value>
  </Item>
  <Item>
    <Code>MyCode</Code>
    <Value>MyValue</Value>
  </Item>
  <Item>
    <Code>AnotherItem</Code>
    <Value>Another value</Value>
  </Item>
</Items>

XPath: select a node based on another node?

2 Answers2

Linked