TPT: Cannot create relationship between derived classes using base's relationship

[eraffel-MDSol]

I think the model will make it more obvious, but I'm having issues mapping the relationship between two derived classes, using the underlying relationship between the base classes.

Steps to reproduce

Try to create a migration using the following context and entities

    public class MyContext : DbContext
    {
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Parent>().ToTable("Parent");
            modelBuilder.Entity<ParentBase>().ToTable("ParentBase");

            modelBuilder.Entity<Child>().ToTable("Child");
            modelBuilder.Entity<ChildBase>().ToTable("ChildBase");

            modelBuilder.Entity<Child>()
                .HasOne(c => c.Parent)
                .WithMany(p => p.Children)
                .HasPrincipalKey(parent => parent.Id)
                .HasForeignKey(c => c.BaseParentId);
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseSqlServer("Server=localhost;Database=Test;Trusted_Connection=True;");
        }
    }

    public abstract class ParentBase
    {
        public Guid Id { get; set; }
    }

    public class Parent : ParentBase
    {
        public List<Child> Children { get; set; }
    }

    public abstract class ChildBase
    {
        public Guid Id { get; set; }
        public ParentBase BaseParent { get; set; }

        public Guid BaseParentId { get; set; }
    }

    public class Child : ChildBase
    {
        public Parent Parent { get; set; }
    }

When I try to create a migration, I get the following.

System.ArgumentNullException: Value cannot be null. (Parameter 'key')
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.SharedTableConvention.TryUniquifyForeignKeyNames(IConventionEntityType entityType, Dictionary`2 foreignKeys, StoreObjectIdentifier& storeObject, Int32 maxLength)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.SharedTableConvention.ProcessModelFinalizing(IConventionModelBuilder modelBuilder, IConventionContext`1 context)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ImmediateConventionScope.OnModelFinalizing(IConventionModelBuilder modelBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.OnModelFinalizing(IConventionModelBuilder modelBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Model.FinalizeModel()
   at Microsoft.EntityFrameworkCore.ModelBuilder.FinalizeModel()
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.CreateModel(DbContext context, IConventionSetBuilder conventionSetBuilder, ModelDependencies modelDependencies)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.GetModel(DbContext context, IConventionSetBuilder conventionSetBuilder, ModelDependencies modelDependencies)
   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.Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<System.IServiceProvider>.get_Instance()
   at Microsoft.EntityFrameworkCore.Infrastructure.Internal.InfrastructureExtensions.GetService[TService](IInfrastructure`1 accessor)
   at Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Exe

Further technical details

EF Core version: 5.0.0-rc.1.20414.1
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: NET Core 3.1
Operating system: Windows 10
IDE: Visual Studio 2019 16.7.1

[eraffel-MDSol]

It's not throwing an error anymore, but it's creating both a BaseParentId and BaseParentId1 column, and it's creating a FK from ChildBase to Parent, which also wouldn't be desired.

[AndriySvyryd]

but it's creating both a BaseParentId and BaseParentId1 column

You need to configure the base relationship or remove BaseParent to avoid that

            modelBuilder.Entity<ChildBase>()
                .HasOne(c => c.BaseParent)
                .WithMany()
                .HasPrincipalKey(parent => parent.Id)
                .HasForeignKey(c => c.BaseParentId);

and it's creating a FK from ChildBase to Parent, which also wouldn't be desired.

You can remove it in the generated migration

[eraffel-MDSol]

Yes, that worked. Thank you!

[eraffel-MDSol]

@AndriySvyryd I didn't notice this cause I wasn't logging to console, but this is generating the warning from this: #22175

The foreign key {'BaseParentId'} on the entity type 'Child' targeting 'Parent' cannot be represented in the database. Either the properties {'BaseParentId'} aren't mapped to table 'Child' or the principal properties {'Id'} aren't mapped to table 'Parent'. All foreign key properties must map to the table that the dependent type is mapped to and all principal properties must map to a single table that the principal type is mapped to.

but I can't tell if there are actually any issues, or if I should ignore the error message

for the record, the current context:

   public class MyContext : DbContext
    {
        public DbSet<Parent> Parents { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Parent>().ToTable("Parent");
            modelBuilder.Entity<ParentBase>().ToTable("ParentBase");

            modelBuilder.Entity<Child>().ToTable("Child");
            modelBuilder.Entity<ChildBase>().ToTable("ChildBase");

            modelBuilder.Entity<ChildBase>()
                .HasOne(c => c.BaseParent)
                .WithMany()
                .HasPrincipalKey(parent => parent.Id)
                .HasForeignKey(c => c.BaseParentId);

            modelBuilder.Entity<Child>()
                .HasOne(c => c.Parent)
                .WithMany(p => p.Children)
                .HasPrincipalKey(parent => parent.Id)
                .HasForeignKey(c => c.BaseParentId);
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseSqlServer("Server=localhost;Database=Test;Trusted_Connection=True;");
            optionsBuilder.LogTo(Console.WriteLine);
        }
    }

    public abstract class ParentBase
    {
        public Guid Id { get; set; }
    }

    public class Parent : ParentBase
    {
        public List<Child> Children { get; set; }
    }

    public abstract class ChildBase
    {
        public Guid Id { get; set; }
        public ParentBase BaseParent { get; set; }

        public Guid BaseParentId { get; set; }
    }

    public class Child : ChildBase
    {
        public Parent Parent { get; set; }
    }

[AndriySvyryd]

@eraffel-MDSol You can ignore it, since you are configuring two relationships one of them will be created in the database