Issues with multilevel inheritance and TPH - The entity type is part of a hierarchy, but does not have a discriminator value configured.

[bjorkstromm]

I'm porting an application from EF Core 2.2 to 3.0 an hitting a issue with multilevel inheritance and TPH. Note, this used to work fine with with v2.2, but now the model validator throws exception:
The entity type 'Foo' is part of a hierarchy, but does not have a discriminator value configured.

This happens when i have an additional abstract class in the inheritance chain.

Classes (see full repro below):

abstract class A { }
class B : A { }
abstract class C : A { }
class D : C { }
class E : C { }

Steps to reproduce

A simplified repro.

using System;
using System.ComponentModel.DataAnnotations;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace efcorerepro
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var ctx = new MyContext();

            _ = await ctx.A.ToListAsync();
        }
    }

    public class MyContext : DbContext
    {
        public DbSet<A> A { get; set;}

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"Server=(localdb)\MSSQLLocalDB;Integrated Security=true");

            base.OnConfiguring(optionsBuilder);
        }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            builder.Entity<A>(x => {
                x.HasKey(m => m.Id);

                x.HasDiscriminator<int>("Type")
                    .HasValue<B>(1)
                    .HasValue<D>(2)
                    .HasValue<E>(3);
            });
            builder.Entity<B>(x => x.HasBaseType<A>());
            builder.Entity<C>(x => x.HasBaseType<A>());
            builder.Entity<D>(x => x.HasBaseType<C>());
            builder.Entity<E>(x => x.HasBaseType<C>());
        }
    }

    public abstract class A
    {
        [Key]
        public Guid Id { get; set;}
        public string PropA { get; set; }
    }

    public class B : A
    {
        public string PropB { get; set; }
    }

    public abstract class C : A
    {
        public string PropC { get; set; }
    }

    public class D : C
    {
        public string PropD { get; set; }
    }

    public class E : C
    {
        public string PropE { get; set; }
    }
}

Throws following exception:

System.InvalidOperationException
  HResult=0x80131509
  Message=The entity type 'D' is part of a hierarchy, but does not have a discriminator value configured.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelValidator.ValidateDiscriminatorValues(IEntityType rootEntityType)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelValidator.ValidateDiscriminatorValues(IModel model, IDiagnosticsLogger`1 logger)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelValidator.Validate(IModel model, IDiagnosticsLogger`1 logger)
   at Microsoft.EntityFrameworkCore.Infrastructure.RelationalModelValidator.Validate(IModel model, IDiagnosticsLogger`1 logger)
   at Microsoft.EntityFrameworkCore.SqlServer.Internal.SqlServerModelValidator.Validate(IModel model, IDiagnosticsLogger`1 logger)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.ValidatingConvention.ProcessModelFinalized(IConventionModelBuilder modelBuilder, IConventionContext`1 context)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ImmediateConventionScope.OnModelFinalized(IConventionModelBuilder modelBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.OnModelFinalized(IConventionModelBuilder modelBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Model.FinalizeModel()
   at Microsoft.EntityFrameworkCore.ModelBuilder.FinalizeModel()
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.CreateModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.<>c__DisplayClass5_0.<GetModel>b__1()
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.get_Value()
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.GetModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.CreateModel()
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.get_Model()
   at Microsoft.EntityFrameworkCore.Infrastructure.EntityFrameworkServicesBuilder.<>c.<TryAddCoreServices>b__7_3(IServiceProvider p)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
   at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
   at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
   at Microsoft.EntityFrameworkCore.DbContext.get_Model()
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityType()
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.CheckState()
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityQueryable()
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.System.Collections.Generic.IAsyncEnumerable<TEntity>.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.<ToListAsync>d__64`1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at efcorerepro.Program.<Main>d__0.MoveNext() in C:\src\tmp\efcorerepro\Program.cs:line 16

Further technical details

EF Core version: 3.0.0
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET Core 3.0
Operating system: Windows 10
IDE: Visual Studio 2019 16.3

[AndriySvyryd]

Duplicate of #18385
The workaround is to move the entity C configuration before entity A

[bjorkstromm]

@AndriySvyryd Thanks for the quick reply! Workaround seemed to work! Thank you!