Entity Framework 4.3 - TPH mapping and migration error

Question

I\'m using Entity Framework 4.3 with code first and manual migrations. I\'m trying to map a TPH (table-per-hierarchy) setup which uses two custom discriminator fields. One f

Answer 1

This is a known issue with 4.3 and 4.3.1. (We found it too late to put the fix in 4.3.1.) Luckily there is a fairly simple way to change your code that should make it work.

In a nutshell, you used to be able to make chained map calls on a single EntityConfiguration in 4.1. and 4.2. Something like this pattern:

modelBuilder.Entity<Parent>()
    .Map<Foo>(...)
    .Map<Bar>(...);

This doesn't work in 4.3 and instead you have to make each Map call on an EntityConfiguration for that entity. So a pattern something like this:

modelBuilder.Entity<Foo>()
   .Map<Foo>(...);

modelBuilder.Entity<Bar>()
   .Map<Bar>(...);

Taking your case specifically, this should work:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<ParentClass>()
        .ToTable("Parent");

    modelBuilder.Entity<Foo>()
        .Map(m =>
                {
                    m.Requires("IsActive").HasValue(1);
                    m.Requires("Type").HasValue("Foo");
                });

    modelBuilder.Entity<Bar>()
        .Map(m =>
                {
                    m.Requires("IsActive").HasValue(1);
                    m.Requires("Type").HasValue("Bar");
                });
}

(I've removed a few of the generic parameters since they aren't needed, but that's not important.)

Doing this using explicit EntityConfigurations you would use something like this:

public class ParentConfiguration : EntityTypeConfiguration<ParentClass>
{
    public ParentConfiguration()
    {
        ToTable("Parent");
    }
}

public class FooConfiguration : EntityTypeConfiguration<Foo>
{
    public FooConfiguration()
    {
        Map(m =>
        {
            m.Requires("IsActive").HasValue(1);
            m.Requires("Type").HasValue("Foo");
        });
    }
}

public class BarConfiguration : EntityTypeConfiguration<Bar>
{
    public BarConfiguration()
    {
        Map(m =>
        {
            m.Requires("IsActive").HasValue(1);
            m.Requires("Type").HasValue("Bar");
        });
    }
}

And then

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Configurations
        .Add(new ParentConfiguration())
        .Add(new FooConfiguration())
        .Add(new BarConfiguration());
}

We plan to fix this in 5.0.