Question

I am working on a project in ASP.NET MVC using EF4 Code-First for the modeling. I have the following model classes:

public class ComicBook
{
    public long ComicBookID { get; set; }
    public string IssueTitle { get; set; }
    public int IssueNumber { get; set; }
    public DateTime PublishDate { get; set; }

    public IList<ComicBookPerson> Writers { get; set; }
    public IList<ComicBookPerson> Pencillers { get; set; }

    public IList<User> CollectingUsers { get; set; }
}

public class ComicBookPerson
{
    public long ComicBookPersonID { get; set; }
    public string Name { get; set; }

    public IList<ComicBook> WorkedOnComicBooks { get; set; }
}

public class User
{
    [Key]
    public long UserID { get; set; }
    public string Email { get; set; }

    public IList<ComicBook> CollectedBooks { get; set; }
}

And the following DbContext:

public class ComicContext : DbContext
{
    public DbSet<ComicBook> ComicBooks { get; set; }
    public DbSet<ComicBookPerson> ComicBookPerson { get; set; }
    public DbSet<User> Users { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<ComicBook>()
            .HasMany(b => b.Writers)
            .WithMany(w => w.WorkedOnComicBooks)
            .Map(t => t.MapLeftKey("ComicBookID")
                .MapRightKey("WriterID")
                .ToTable("ComicBook_Writers"));

        modelBuilder.Entity<ComicBook>()
            .HasMany(b => b.Pencillers)
            .WithMany(p => p.WorkedOnComicBooks)
            .Map(t => t.MapLeftKey("ComicBookID")
                .MapRightKey("PencillerID")
                .ToTable("ComicBook_Penciller"));
    }
}

The rules that need to apply are:

• Users can have many ComicBooks in their collection
• ComicBooks can be in many users’ collections
• Each ComicBook can have 1 or more Writers
• Each ComicBook can have 1 or more Pencillers
• A ComicBookPerson can be a Writer or a Penciller on any book
• A ComicBookPerson can work on many books, as a Writer, Penciller, or both

The many-to-many schema between Users and ComicBooks is created fine. It is the many-to-many between ComicBooks and ComicBookPersons that is breaking. The error message I get is:

Schema specified is not valid. Errors: 
(15,6) : error 0040: Type ComicBook_Writers is not defined in namespace Comics.Models (Alias=Self).

I basically want two join tables, one called ComicBook_Writers and one called ComicBookPencillers. Both tables will contain a ComicBookID and a ComicBookPersonID. Is this possible in EF Code First?

Answer 1

You need two collection properties in ComicBookPerson class that relates to writers and pencillers.

public class ComicBookPerson
{
    public long ComicBookPersonID { get; set; }
    public string Name { get; set; }

    public IList<ComicBook> WroteComicBooks { get; set; }
    public IList<ComicBook> PenciledComicBooks { get; set; }
}

Model mapped as

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<ComicBook>()
        .HasMany(b => b.Writers)
        .WithMany(w => w.WroteComicBooks)
        .Map(t => t.MapLeftKey("ComicBookID")
            .MapRightKey("WriterID")
            .ToTable("ComicBook_Writers"));

    modelBuilder.Entity<ComicBook>()
        .HasMany(b => b.Pencillers)
        .WithMany(p => p.PenciledComicBooks)
        .Map(t => t.MapLeftKey("ComicBookID")
            .MapRightKey("PencillerID")
            .ToTable("ComicBook_Penciller"));
}