Query an XDocument for elements by name at any depth

user_53501 0
Viewed 281743

I have an XDocument object. I want to query for elements with a particular name at any depth using LINQ.

When I use Descendants("element_name"), I only get elements that are direct children of the current level. I'm looking for the equivalent of "//element_name" in XPath...should I just use XPath, or is there a way to do it using LINQ methods?

linq-to-xml xml linq .net c#
10 Answers

Descendants should work absolutely fine. Here's an example:

using System;
using System.Xml.Linq;

class Test
{
    static void Main()
    {
        string xml = @"
<root>
  <child id='1'/>
  <child id='2'>
    <grandchild id='3' />
    <grandchild id='4' />
  </child>
</root>";
        XDocument doc = XDocument.Parse(xml);

        foreach (XElement element in doc.Descendants("grandchild"))
        {
            Console.WriteLine(element);
        }
    }
}

Results:

<grandchild id="3" />
<grandchild id="4" />

user_226560

An example indicating the namespace:

String TheDocumentContent =
@"
<TheNamespace:root xmlns:TheNamespace = 'http://www.w3.org/2001/XMLSchema' >
   <TheNamespace:GrandParent>
      <TheNamespace:Parent>
         <TheNamespace:Child theName = 'Fred'  />
         <TheNamespace:Child theName = 'Gabi'  />
         <TheNamespace:Child theName = 'George'/>
         <TheNamespace:Child theName = 'Grace' />
         <TheNamespace:Child theName = 'Sam'   />
      </TheNamespace:Parent>
   </TheNamespace:GrandParent>
</TheNamespace:root>
";

XDocument TheDocument = XDocument.Parse( TheDocumentContent );

//Example 1:
var TheElements1 =
from
    AnyElement
in
    TheDocument.Descendants( "{http://www.w3.org/2001/XMLSchema}Child" )
select
    AnyElement;

ResultsTxt.AppendText( TheElements1.Count().ToString() );

//Example 2:
var TheElements2 =
from
    AnyElement
in
    TheDocument.Descendants( "{http://www.w3.org/2001/XMLSchema}Child" )
where
    AnyElement.Attribute( "theName" ).Value.StartsWith( "G" )
select
    AnyElement;

foreach ( XElement CurrentElement in TheElements2 )
{
    ResultsTxt.AppendText( "\r\n" + CurrentElement.Attribute( "theName" ).Value );
}
user_1276380

Descendants will do exactly what you need, but be sure that you have included a namespace name together with element's name. If you omit it, you will probably get an empty list.

user_220620

This my variant of the solution based on LINQ and the Descendants method of the XDocument class

using System;
using System.Linq;
using System.Xml.Linq;

class Test
{
    static void Main()
    {
        XDocument xml = XDocument.Parse(@"
        <root>
          <child id='1'/>
          <child id='2'>
            <subChild id='3'>
                <extChild id='5' />
                <extChild id='6' />
            </subChild>
            <subChild id='4'>
                <extChild id='7' />
            </subChild>
          </child>
        </root>");

        xml.Descendants().Where(p => p.Name.LocalName == "extChild")
                         .ToList()
                         .ForEach(e => Console.WriteLine(e));

        Console.ReadLine();
    }
}

Results:

For more details on the Desendants method take a look here.

user_90910390

We know the above is true. Jon is never wrong; real life wishes can go a little further.

<ota:OTA_AirAvailRQ
    xmlns:ota="http://www.opentravel.org/OTA/2003/05" EchoToken="740" Target=" Test" TimeStamp="2012-07-19T14:42:55.198Z" Version="1.1">
    <ota:OriginDestinationInformation>
        <ota:DepartureDateTime>2012-07-20T00:00:00Z</ota:DepartureDateTime>
    </ota:OriginDestinationInformation>
</ota:OTA_AirAvailRQ>

For example, usually the problem is, how can we get EchoToken in the above XML document? Or how to blur the element with the name attribute.

  1. You can find them by accessing with the namespace and the name like below

     doc.Descendants().Where(p => p.Name.LocalName == "OTA_AirAvailRQ").Attributes("EchoToken").FirstOrDefault().Value

  2. You can find it by the attribute content value, like this one.

user_9142840
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