Projections with Entity Framework

Question

I have a question about making projections with the Entity Framework.

I have three tables: Profile, Biography and BiographyTranslation

I want to do the following projection: (biographies = IQueryable)

return biographies.Select(b => new ProfileBiography
                               {
                                 Id = b.BiographieID,
                                 OwnerId = b.Profile.ProfileID,
                                 Translations = 
                              b.Translations.Select(t => new DocumentTranslation()
                                           {
                                             DocumentId = b.BiographieID,
                                             FileName = t.BiographyTextFile,
                                             Title = t.Title,
                                             Text = t.Text,
                                             LanguageId = t.LanguageID
                                           })
                                }

My Problem: The OwnerId is projected correctly, but the number of translations are always 0.

Does projection not work on collection properties?

I also tried biographies.Inlcude("Translations"), but the result was the same.

UPDATE

I created a small Test Project you can find here:

TestProject.zip

Just 3 tables (create and insert statements included),an EDMX file and a class to load biographies. I still can't get it to work to project a collection navigation property, simple navigation properties work fine. Maybe someone can see from the test project what I'm doing wrong....

UPDATE

I tried a new approach, but still no luck:

using (var context = new DatabaseEntities())
        {
            return context.BiographySets
                .Where(bio => bio.ProfileId == profileId)
                .Select(bio => new DocumentModel()
                {
                    Id = bio.Id,
                    OwnerId = bio.Profile.Id,
                    Translations = context.BiographyTranslationSets.Where(t => t.BiographyId == bio.Id)
                        .Select(t => new DocumentTranslation()
                        {
                            DocumentId = bio.Id,
                            LanguageId = t.LanguageId,
                            Text = t.Text
                        })
                }).ToList();
        }

UPDATE

If I use an anonymous type it surprisingly works...

using (var context = new DatabaseEntities())
        {
            return context.BiographySets
                .Where(bio => bio.ProfileId == profileId)
                .Select(bio => new 
                {
                    Id = bio.Id,
                    OwnerId = bio.Profile.Id,
                    Translations = bio.Translations
                                           .Select(t => new 
                                           {
                                               DocumentId = bio.Id,
                                               LanguageId = t.LanguageId,
                                               Text = t.Text
                                           })
                }).ToList();
        }

Answer 1

Ok, I found the problem:

this was my class for the DocumentModel:

public class DocumentModel
{
    public DocumentModel()
    {
        _translations = new List<DocumentTranslation>();
    }

    public int Id { get; set; }

    public int OwnerId { get; set; }

    private List<DocumentTranslation> _translations;
    public IEnumerable<DocumentTranslation> Translations
    {
        get { return _translations; }
        set { _translations = value.ToList(); }
    }
}

And here was the problem:

set { _translations = value.ToList(); }

I can't call ToList() in my Setter because it will break the query.