What is the LINQ to XML equivalent for this XPath

Question

I wondering what the "best practice" way (in C#) is to implement this xpath query with LINQ:

/topNode/middleNode[@filteringAttribute='filterValue']/penultimateNode[@anotherFilterAttribute='somethingElse']/nodesIWantReturned

I would like an IEnumerable list of the 'nodesIWantReturned', but only from a certain section of the XML tree, dependent on the value of ancestor attributes.

Possible duplicate of [How to use XPath with XElement or LINQ?](http://stackoverflow.com/questions/3642829/how-to-use-xpath-with-xelement-or-linq) — Michael Freidgeim, Sep 01 '16 at 07:12

score 10 · Answer 1 · answered Jan 15 '09 at 23:39

10

In addition to the Linq methods shown, you can also import the System.Xml.XPath namespace and then use the XPathSelectElements extension method to use your XPath query directly.

It is noted in the class that these methods are slower than 'proper' Linq-to-XML, however a lot of the time this isn't too important, and sometimes it's easier just to use XPath (it's certainly a lot terser!).

var result = doc.XPathSelectElements("your xpath here");

answered Jan 15 '09 at 23:39

Greg Beech

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Thank you! Great tip! Will note that this is slower. – Torbjörn Hansson Jul 20 '10 at 08:50

Mehrdad Afshari · Answer 2 · 2009-02-27T10:38:34.270

3

var result = root.Elements("topNode")
                 .Elements("middleNode")
                 .Where(a => (string)a.Attribute("filteringAttribute") == "filterValue")
                 .Elements("penultimateNode")
                 .Where(a => (string)a.Attribute("anotherFilterAttribute") == "somethingElse")
                 .Elements("nodesIWantReturned");

edited Feb 27 '09 at 10:38

answered Jan 15 '09 at 22:37

Mehrdad Afshari

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Wouldn't it be safer to use .Elements instead of .Descendants for the first three node selections? .Descendents could reach too far if the content of nodesIWantReturned has a match? – Kev Jan 15 '09 at 22:58
Huh, yes. Thanks. Looks like I'm sleepy :) Editing – Mehrdad Afshari Jan 15 '09 at 23:15

score 0 · Accepted Answer · answered Jan 15 '09 at 23:30

0

A more verbal solution:

var nodesIWantReturned = from m in doc.Elements("topNode").Elements("middleNode")
              from p in m.Elements("penultimateNode")
              from n in p.Elements("nodesIWantReturned")
              where m.Attribute("filteringAttribute").Value == "filterValue"
              where p.Attribute("anotherFilterAttribute").Value == "somethingElse"
              select n;

answered Jan 15 '09 at 23:30

bruno conde

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This won't work correctly. It'll throw a NullReferenceException if an element is encountered that lacks the attribute. – Mehrdad Afshari Jan 16 '09 at 13:17

What is the LINQ to XML equivalent for this XPath

3 Answers3