Entity Framework Core–Table per hierarchy

In my Entity Framework Core application I wanted to use the Table Per Hierarchy pattern. So I configured the EF mapping to use a discriminator column:

	public class MyDbContext: DbContext
	{
	protected override void OnModelCreating(ModelBuilder builder)
	{
	builder.Entity<Supplier>(b =>
	{
	b.ToTable("Supplier");
	b.HasDiscriminator(x=> x.SupplierType);
	})
	}
	}

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This didn’t had the desired effect. As I ran my application I got the following error message:

The entity type 'ForeignSupplier' is part of a hierarchy, but does not have a discriminator value configured.

Whoops! I forgot to specify how EF Core should recognize the different child types. Let’s fix this in our configuration:

	public class MyDbContext: DbContext
	{
	protected override void OnModelCreating(ModelBuilder builder)
	{
	builder.Entity<Supplier>(b =>
	{
	b.ToTable("Supplier");
	b.HasDiscriminator(x=> x.SupplierType)
	.HasValue<DomesticSupplier>(SupplierType.Domestic)
	.HasValue<ForeignSupplier>(SupplierType.Foreign);
	})
	}
	}

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