Question

Im having some trouble with a linq query into an xml tree. Here is what the tree structure looks like:

<Student>
  <ID> Hello </Hello>
  <Classroom>
     <Name> 1B </Name>
     <Year> 1 </Year>
  </Classroom>
  <Classroom>
     <Name> 2B </Name>
     <Year> 2 </Year>
  </Classroom>
  <Classroom>
     <Name> 3B </Name>
     <Year> 3 </Year>
  </Classroom>
</Student>

Now this is one student entry among 5. say i am passed an XElement Student node from another method and i want to search for a classroom given the XElement Student node and the classroom name. So i have to write a method like this:

getClassRoomNode(XElement StudentNode, string classroomName)

This is what ive tried. Please let me know where i am wrong

XElement classroom = StudentNode.Descendants("Classroom")
                                .Where(arg => arg.Element("Name").Value == classroomName)
                                .Select(arg => arg.Parent)
                                .First();

This returns the StudentNode back again instead of a classroom node. Can anyone please help me out with this?

Answer 1

You don’t need to select parent, just the get the First(), or even better Single() class room.

XElement classroom = StudentNode.Descendants("Classroom")
    .Single(arg => arg.Element("Name").Value == classroomName);

I suggest it is better to error rather than ignore subsequent matches. If the intention is to match the first of many matches then obviously,

XElement classroom = StudentNode.Descendants("Classroom")
    .First(arg => arg.Element("Name").Value == classroomName);