Does EF Core support an abstract base entity which is generic?
c# ef-code-first ef-fluent-api entity-framework entity-framework-core
Question
I remember there were problems with generic entities in previous EF. How about EF Core? I can't find docs related to this matter.
For example:
public abstract class Parent<TEntity> {
public int EntityId { get; set; }
public TEntity Entity { get; set; }
}
public class Child : Parent<Foo> {
}
public class OtherChild : Parent<Bar> {
}
// config for child entities includes this:
config.HasKey(c => c.EntityId);
Though this throws stating that child entities do not define a primary key, when they clearly do!
I can fix this by making Parent non-generic.
Are there official docs for this? Am I doing something wrong, or is this the expected behavior?
Accepted Answer
I can use this model in ef-core 1.1.0:
public abstract class Parent<TEntity>
{
public int EntityId { get; set; }
public TEntity Entity { get; set; }
}
public class Child : Parent<Foo>
{
}
public class OtherChild : Parent<Bar>
{
}
public class Foo
{
public int Id { get; set; }
}
public class Bar
{
public int Id { get; set; }
}
With this mapping in the context:
protected override void OnModelCreating(ModelBuilder mb)
{
mb.Entity<Child>().HasKey(a => a.EntityId);
mb.Entity<Child>().HasOne(c => c.Entity).WithMany().HasForeignKey("ParentId");
mb.Entity<OtherChild>().HasKey(a => a.EntityId);
mb.Entity<OtherChild>().HasOne(c => c.Entity).WithMany().HasForeignKey("ParentId");
}
Which leads to this fantastic model:
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