Question

I am looking for a linq to Xdoc query to group by a subset of the XML nodes. I’ve only been able to get this working to return a subset of the data but I need the entire xml document passed back with only the particular nodes grouped.

<Root>
  <Elementname1>
  </Elementname1>
  <Elementname2>
  </Elementname2>
  <Elementname3 attrname="test1">
    <Child>
    </Child>
  </Elementname3>
  <Elementname3 attrname="test1">
    <Child>
    </Child>
  </Elementname3>
</Root>

This code:

var result =
        from row in xDoc.Descendants("Elementname3")
        group row by (string)row.Attribute("attrname") into g
        select g.First();

returns:

<Elementname3 attrname="test1">
 <Child></Child>
</Elementname3>

Expecting:

<Root>
  <Elementname1>
  </Elementname1>
  <Elementname2>
  </Elementname2>
  <Elementname3 attrname="test1">
    <Child>
    </Child>
  </Elementname3>
</Root>

I understand since descendant element is starting at elementname3; just not sure on how to expound the linq query to start with the root node and group as expected.

Answer 1

Try this:

var result = new XDocument(
    new XElement("Root",
        from x in doc.Root.Elements()
        group x by new { x.Name, Attr = (string)x.Attribute("attrname") } into g
        select g.First()
    )
);