I’m constantly amazed by the power and simplicity of LINQ. I love that I can turn a flat table into a object graph with a couple of view models and a single LINQ query.
Given a repository method that returns a list of Tracks based on the following SQL:
Select Id, Title, Artist, Album, Year, TrackNumber, FilePathName From Track Order By Artist, Album, TrackNumber, Title
We can create a nice hierarchy of Artists, each with 0 or more albums, of which each may have a number of tracks – with a nice, neat LINQ query:
var artists = _libraryRepository.FetchLibrary()
.AsParallel()
.GroupBy(track => track.Artist)
.Select(group => new Artist(group.Key,
group.GroupBy(track2 => track2.Album)
.Select(group2 => new Album(group2.Key,group2)))
);
And the models:
public class Artist
{
public string Name { get; set; }
public IEnumerable<Album> Albums { get; private set; }
public Artist() { }
public Artist(string name, IEnumerable<Album> albums)
{
Name = name;
Albums = albums;
}
}
public class Album
{
public string Name { get; set; }
public IEnumerable<Track> Tracks { get; private set; }
public Album() { }
public Album(string name, IEnumerabl<Track> tracks)
{
Name = name;
Tracks = tracks;
}
}
public class Track
{
public Guid Id { get; private set;}
public string Title { get; set; }
public string Artist { get; set; }
public string Album { get; set; }
public string FilePathName { get; set; }
public int? Year { get; set; }
public int? TrackNumber { get; set; }
public Track() {}
public Track(Guid id, string filePathName)
{
Id = id;
FilePathName = filePathName;
}
}
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