EF stores subset of records into another table - entity-framework

Question

I have a header-child tables with the child having different types but stored in the same table (TPH).
On top of this, user can snapshot a copy of a header and its children records and I would like to store the snapped copy into a different table since these snapshot records would be less frequent to view/modify.
To achieve this, I am mixing TPC to my existing TPH.
The new structure is as follows:
public class Header
{
private IList<Child> _childs = new List<Child>();
private IList<ChildSnapshot> _childSnapshots = new List<ChildSnapshot>();
[Key]
public int Id { get; set; }
public string Name { get; set; }
public IList<Child> Childs { get { return _childs; } }
public IList<ChildSnapshot> ChildSnapshots { get { return _childSnapshots; } }
}
public abstract class ChildBase
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
public string Name { get; set; }
[ForeignKey("Header")]
public int HeaderId { get; set; }
[ForeignKey("HeaderId")]
public virtual Header Header { get; set; }
}
public abstract class Child : ChildBase
{
}
public class Child1 : Child
{
}
public class Child2 : Child
{
}
public abstract class ChildSnapshot : ChildBase
{
}
public class ChildSnapshot1 : ChildSnapshot
{
}
public class ChildSnapshot2 : ChildSnapshot
{
}
And the database context:
public class TestContext : DbContext
{
public DbSet<Header> Headers { get; set; }
public DbSet<Child> Childs { get; set; }
public DbSet<ChildSnapshot> ChildSnapshots { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Header>().Map(m => m.ToTable("Header"));
modelBuilder.Entity<Child>()
.Map<Child>(m =>
{
m.MapInheritedProperties();
m.ToTable("Child");
})
.Map<Child1>(m =>
{
m.Requires("Discriminator").HasValue("Child1");
})
.Map<Child2>(m =>
{
m.Requires("Discriminator").HasValue("Child2");
});
modelBuilder.Entity<ChildSnapshot>()
.Map<ChildSnapshot>(m =>
{
m.MapInheritedProperties();
m.ToTable("ChildSnapshot");
})
.Map<ChildSnapshot1>(m =>
{
m.Requires("Discriminator").HasValue("Child1");
})
.Map<ChildSnapshot2>(m =>
{
m.Requires("Discriminator").HasValue("Child2");
});
}
}
It works perfectly after many trials and errors. However, I've got to create 2 list properties in Header class. Is it possible to have only 1 list property of ChildBase type? I got the following error when I do so.
The type 'Child' cannot be mapped as defined because it maps inherited
properties from types that use entity splitting or another form of
inheritance. Either choose a different inheritance mapping strategy so
as to not map inherited properties, or change all types in the
hierarchy to map inherited properties and to not use splitting.
Why is the behaviour determined by the type of the container list? Can't EF infer from the type of the object in the list instead?
FYI I am using EF 4.3.