How Model n--n relationship in EF Code First to automatically generated views work correctly?

Question

I use EF Code First and have a problem in n-n relationship, assume we have a singer that sing in some genres, so we need this models: Artist, Genre, and ArtistsGenres, I def

Answer 1

You haven't to create a separate Model for association between to models in a many-to-many relationship. Really the ArtistsGenres is not necessary. So, remove it, and you just have to change your modelBuilder to this one:

modelBuilder.Entity()
    .HasMany(c => c.Genres)
    .WithMany(x => x.Artists)
    .Map(a => {
        a.ToTable("ArtistsGenres");
        a.MapLeftKey("ArtistId");
        a.MapRightKey("GenreId");
    });

It will use the ArtistsGenres table to map a many-to-many relationship between Artists table and Genres table automatically.

Note: When you define the ArtistsGenres model, EF will not look at it as a relationship, because you tell him that Hey EF, I have another model named ArtistsGenres! Please manage it for me!!!

Your new entities and dbcontext will be these:

public class Artist {
    public long Id { get; set; }
    public string Name { get; set; }
    public ICollection Genres { get; set; }
}

public class Genre {
    public long Id { get; set; }
    public string Title { get; set; }
    public ICollection Artists { get; set; }
}

public class MusicDB : DbContex {

    public DbSet Artists { get; set; }
    public DbSet Genres { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder) {
    modelBuilder.Entity()
        .HasMany(c => c.Genres)
        .WithMany(x => x.Artists)
        .Map(a => {
            a.ToTable("ArtistsGenres");
            a.MapLeftKey("ArtistId");
            a.MapRightKey("GenreId");
        });

}

Let me know if you have any questions or need clarifications on any part.