LinqToSQl and adapting from linq to Domain objects in a centralised manner - linq-to-sql

Question

Imagine the following code:
return from a in DBContext.Acts
join artist in DBContext.Artists
on a.ArtistID equals artist.ID into art
from artist in art.DefaultIfEmpty()
select new Shared.DO.Act {
ID = a.ID,
Name = a.Name,
Artist = new Shared.DO.Artist {
ID = artist.ID,
Name = artist.Name
},
GigId = a.GigID
};
As you can see, the linqtosql generated act object is adapted into the Shared.DO.Act object. As part of this a linqtosql generated Artist object is adapted into a Shared.DO.Artist
Elsewhere in my code base, I may want to request an Artist (see below):
return from a in DBContext.Artists
select new Shared.DO.Artist {
ID = artist.ID,
Name = artist.Name
},
GigId = a.GigID
};
This means the adption code for an Artist now appears in two places! Once when getting an artist and also when an act is loaded
How should I centralise this adaption code?

Answer 1

I would do this using an Artists class with a dictionary of artists:
public class Artists
{
// key should be whatever type artist.ID is
private Dictionary<int, Shared.DO.Artist> _artistDictionary;
public static Get(int id)
{
if (_artistDictionary == null)
_artistDictionary = new Dictionary<int, Shared.DO.Artist>();
if (!_artistDictionary.ContainsKey(id))
{
var artist = from a in DBContext.Artists
on a.ID equals id
select new Shared.DO.Artist {
ID = a.ID,
Name = a.Name
};
_artistDictionary.Add(id, artist);
}
return _artistDictionary[id];
}
}