Question

I have two classes – Cd and Track which I’m trying to read into from a XML file using Linq.

public Cd(string t, string a, string cat, DateTime rls, Track[] tr)
public Track(string t, int l)

The XML looks like this.

<media>
  <cd>
    <artist>Ozzy Osbourne</artist>
    <album Name="Bark at the moon" Type="Metal" Tracks="5" ReleaseDate="1983-12-10">
      <track Length="300">Bark at the moon</track>
      <track Length="235">You're No Different</track>
      <track Length="567">Now You See It (Now You Don't)</track>
      <track Length="356">Rock 'N' Roll Rebel</track>
      <track Length="120">Centre of Eternity</track>
    </album>
  </cd>
  <cd>
    <artist>Journey</artist>
    <album Name="Escape" Type="Rock" Tracks="4" ReleaseDate="1981-07-31">
      <track Length="300">Don't Stop Believin'</track>
      <track Length="235">Stone in Love</track>
      <track Length="567">Who's Crying Now</track>
      <track Length="356">Keep on Runnin'</track>
    </album>
  </cd>
</media>

The code I’m trying to use is as follows

XElement xdoc = XElement.Load("dbxml.xml");
    var temp = from cds in xdoc.Descendants("cd")
    select new Cd(
        cds.Element("artist").Value,
        cds.Element("album").Attribute("Name").Value,
        cds.Element("album").Attribute("Type").Value,
        DateTime.Parse(cds.Element("album").Attribute("ReleaseDate").Value),
        new Track[] { // One Track reads fine..
            new Track(cds.Element("album").Element("track").Value,
               int.Parse(cds.Element("album").Element("track").Attribute("Length").Value)) 
               }
        );

The problem is that I don’t know how to initialize the array with all the tracks read from the XML file. I could wrap the whole query in a .ToList(), use an anonomyous type and foreach-it but I’d like to know if there is a way to do this in just one run with linq.

cds.Elements("album").Elements("song") returns an IEnumerable<XElement> collection and somehow that should be added to the array as a range and turned into a string and an int, or something to that affect. Any help out there?

Thanks!

Answer 1

This would work:

XElement xdoc = XElement.Load("test.xml");
var temp = from cds in xdoc.Descendants("cd")
            select new Cd(
                cds.Element("artist").Value,
                cds.Element("album").Attribute("Name").Value,
                cds.Element("album").Attribute("Type").Value,
                DateTime.Parse(cds.Element("album").Attribute("ReleaseDate").Value),
                cds.Element("album").Descendants("track").Select(t => new Track(t.Value, int.Parse(t.Attribute("Length").Value))).ToArray() 
                );

Easier to read (imo) using properties:

select new Cd()
    {
        Artist = cds.Element("artist").Value,
        Album = cds.Element("album").Attribute("Name").Value,
        Type = cds.Element("album").Attribute("Type").Value,
        ReleaseDate = DateTime.Parse(cds.Element("album").Attribute("ReleaseDate").Value),
        Tracks = cds.Element("album")
                    .Descendants("track")
                    .Select(t => new Track()
                    {
                      Name = t.Value,
                      Length = int.Parse(t.Attribute("Length").Value)
                    }).ToArray()
    };

You should consider adding a default constructor to Cd and Track and exposing public properties or use named parameters – this would make the LINQ statement much more readable.