TPH Navigation Properties For Inherited Types

[GravlLift]

I'm using TPH in my application and trying to get multiple navigations on various entities in the hierarchy. I've created a repo to demonstrate the issue I'm facing.

I have 4 entities in my context:

Entity

    public abstract class Entity
    {
        public int Id { get; set; }
        public string TaxIdentifier { get; set; }
        public int? ContactId { get; set; }
        public Contact Contact { get; set; }
    }

Person

    public class Person : Entity
    {
    }

Business

    public class Business : Entity
    {
    }

Contact

    public class Contact
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string PhoneNumber { get; set; }
        public Person Person { get; set; }
        public ICollection<Entity> Entities { get; set; }
    }

My db context describes the nature of the relationship, basically a Person to Contact is 1-1, and Contact to Entity is 1-Many. An Entity is required to have a contact.

AppliocationDbContext

    public class ApplicationDbContext : DbContext
    {
        public DbSet<Contact> Contacts { get; set; }
        public DbSet<Business> Businesses { get; set; }
        public DbSet<Person> People { get; set; }


        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        { }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);


            modelBuilder.Entity<Contact>(
                eb =>
                {
                    eb.HasMany(c => c.Entities)
                        .WithOne(p => p.Contact)
                        .HasForeignKey(p => p.ContactId)
                        .IsRequired();
                    eb.HasOne(c => c.Person)
                        .WithOne(p => p.Contact)
                        .HasForeignKey<Person>(p => p.ContactId)
                        .IsRequired();
                }
            );


            modelBuilder.Entity<Entity>(
                eb =>
                {
                    eb.HasDiscriminator<string>("EntityType");
                }
            );


            modelBuilder.Entity<Business>(
                eb =>
                {
                    eb.HasBaseType<Entity>();
                }
            );


            modelBuilder.Entity<Person>(
                eb =>
                {
                    eb.HasBaseType<Entity>();
                }
            );
        }
    }

I would expect this to model a Contact table and an Entity table with a discriminator and a ContactId column, and populate Contact.Person and Contact.Entities if Included (with a shared object between those two properties if a Person was associated with the Contact).

However, running the reproduction code results in an InvalidOperationException instead:

System.InvalidOperationException: 'Cannot create a relationship between 'Contact.Person' and 'Person.Contact' because a relationship already exists between 'Contact.Entities' and 'Entity.Contact'. Navigation properties can only participate in a single relationship. If you want to override an existing relationship call 'Ignore' on the navigation 'Person.Contact' first in 'OnModelCreating'.'

I was able to hack around this restriction by mapping one of the relationships to a second ContactId column on Entity and then setting up a database trigger that makes the columns mirror each other, updating each other if one is updated.

CREATE TRIGGER [dbo].[TR_ContactId_Mirror] ON [dbo].[Entity] 
AFTER INSERT, UPDATE 
AS  
BEGIN 	
	SET NOCOUNT ON;
	IF (UPDATE([ContactId]))
	BEGIN
		UPDATE E
		SET [ContactId_Mirror] = inserted.[ContactId]
		FROM [dbo].[Entity] E
			INNER JOIN inserted ON E.[Id] = inserted.[Id]
		END
	ELSE IF (UPDATE([ContactId_Mirror]))
	BEGIN
		UPDATE E
		SET [ContactId] = inserted.[ContactId_Mirror]
		FROM [dbo].[Entity] E
			INNER JOIN inserted ON E.[Id] = inserted.[Id]
	END
END

I think it goes without saying that this is very much not an ideal workaround, but I think it demonstrates that what I'm trying to do here is at the very least a valid relational database configuration.

Did I configure something incorrectly, or is this just an unsupported use of EF Core I'm trying to accomplish here?

EF Core version:

Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 5.0
Operating system: Windows 10
IDE: Visual Studio 2019 16.10.2

Error Stack Trace

   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.ThrowForConflictingNavigation(IForeignKey foreignKey, IEntityType principalEntityType, IEntityType dependentEntityType, String navigationToDependent, String navigationToPrincipal)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.GetOrCreateRelationshipBuilder(EntityType principalEntityType, EntityType dependentEntityType, Nullable`1 navigationToPrincipal, Nullable`1 navigationToDependent, IReadOnlyList`1 dependentProperties, IReadOnlyList`1 oldNameDependentProperties, IReadOnlyList`1 principalProperties, Nullable`1 isRequired, Boolean removeCurrent, Nullable`1 principalEndConfigurationSource, Nullable`1 configurationSource, Nullable`1& existingRelationshipInverted)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.ReplaceForeignKey(InternalEntityTypeBuilder principalEntityTypeBuilder, InternalEntityTypeBuilder dependentEntityTypeBuilder, Nullable`1 navigationToPrincipal, Nullable`1 navigationToDependent, IReadOnlyList`1 dependentProperties, IReadOnlyList`1 oldNameDependentProperties, IReadOnlyList`1 principalProperties, Nullable`1 isUnique, Nullable`1 isRequired, Nullable`1 isRequiredDependent, Nullable`1 isOwnership, Nullable`1 deleteBehavior, Boolean removeCurrent, Boolean oldRelationshipInverted, Nullable`1 principalEndConfigurationSource, ConfigurationSource configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.ReplaceForeignKey(ConfigurationSource configurationSource, InternalEntityTypeBuilder principalEntityTypeBuilder, InternalEntityTypeBuilder dependentEntityTypeBuilder, Nullable`1 navigationToPrincipal, Nullable`1 navigationToDependent, IReadOnlyList`1 dependentProperties, IReadOnlyList`1 oldNameDependentProperties, IReadOnlyList`1 principalProperties, Nullable`1 isUnique, Nullable`1 isRequired, Nullable`1 isRequiredDependent, Nullable`1 isOwnership, Nullable`1 deleteBehavior, Boolean removeCurrent, Nullable`1 principalEndConfigurationSource, Boolean oldRelationshipInverted)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.HasNavigations(Nullable`1 navigationToPrincipal, Nullable`1 navigationToDependent, EntityType principalEntityType, EntityType dependentEntityType, ConfigurationSource configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalForeignKeyBuilder.HasNavigations(MemberInfo navigationToPrincipal, MemberInfo navigationToDependent, EntityType principalEntityType, EntityType dependentEntityType, ConfigurationSource configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceNavigationBuilder.WithOneBuilder(MemberIdentity reference)
   at Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceNavigationBuilder.WithOneBuilder(MemberInfo navigationMemberInfo)
   at Microsoft.EntityFrameworkCore.Metadata.Builders.ReferenceNavigationBuilder`2.WithOne(Expression`1 navigationExpression)
   at TBHRepro.Data.ApplicationDbContext.<>c.<OnModelCreating>b__13_0(EntityTypeBuilder`1 eb) in C:\Users\Jason\source\repos\TPHRepro\TPHRepro\Data\ApplicationDbContext.cs:line 29
   at Microsoft.EntityFrameworkCore.ModelBuilder.Entity[TEntity](Action`1 buildAction)
   at TBHRepro.Data.ApplicationDbContext.OnModelCreating(ModelBuilder modelBuilder) in C:\Users\Jason\source\repos\TPHRepro\TPHRepro\Data\ApplicationDbContext.cs:line 22
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelCustomizer.Customize(ModelBuilder modelBuilder, DbContext context)
   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.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.Linq.IQueryable.get_Provider()
   at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
   at TBHRepro.Pages.IndexModel.OnGet() in TPHRepro\TPHRepro\Pages\Index.cshtml.cs:line 25
   at Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.ExecutorFactory.VoidHandlerMethod.Execute(Object receiver, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker.<InvokeHandlerMethodAsync>d__30.MoveNext()

[AndriySvyryd]

This should be possible when #7623 is implemented.