Entity Framework Core Problem with Scaffolding entity with foreign key constraint

Question

Hi I scaffold DbContext from existing database using EF Core. The result context contains 2 related entities in OnModelCreating(..) like this:

modelBuilder.Entity<MauYdc>(entity =>
            {
                entity.HasNoKey();

                entity.ToTable("MauYDC");

                entity.HasIndex(e => e.Idphieu)
                    .HasName("IX_MauYDC")
                    .IsUnique();

                entity.Property(e => e.Idphieu)
                    .HasColumnName("IDphieu")
                    .HasColumnType("numeric(18, 0)")
                    .ValueGeneratedOnAdd();

                entity.Property(e => e.Manv).HasMaxLength(50);

                entity.Property(e => e.Tenphieu)
                    .HasColumnName("tenphieu")
                    .HasMaxLength(100);
            });

modelBuilder.Entity<MauYdcChiTiet>(entity =>
            {
                entity.HasNoKey();

                entity.ToTable("MauYDC_ChiTiet");

                entity.Property(e => e.Id)
                    .HasColumnName("ID")
                    .HasColumnType("numeric(18, 0)")
                    .ValueGeneratedOnAdd();

                entity.Property(e => e.Idphieu)
                    .HasColumnName("IDphieu")
                    .HasColumnType("numeric(18, 0)");

                entity.Property(e => e.Idthuoc).HasColumnName("idthuoc");

                entity.Property(e => e.Soluong).HasColumnName("soluong");

                entity.HasOne(d => d.IdphieuNavigation)
                    .WithMany()
                    .HasPrincipalKey(p => p.Idphieu)
                    .HasForeignKey(d => d.Idphieu)
                    .OnDelete(DeleteBehavior.Cascade)
                    .HasConstraintName("FK_MauYDC_chitiet_MauYDC");
            });

Entity MauYdc

public partial class MauYdc
    {
        public decimal Idphieu { get; set; }
        public string Tenphieu { get; set; }
        public string Manv { get; set; }
    }

Entity MauYdcChiTiet

public partial class MauYdcChiTiet
    {
        public decimal? Idphieu { get; set; }
        public int? Idthuoc { get; set; }
        public double? Soluong { get; set; }
        public decimal Id { get; set; }

        public virtual MauYdc IdphieuNavigation { get; set; }
    }

Those are completely generated by EF Core and I leave them untouched. However, I encounter this error when using other table from the context not related to those two

NullReferenceException: Object reference not set to an instance of an object.
Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.SetOrAddForeignKey(ForeignKey foreignKey, InternalEntityTypeBuilder principalEntityTypeBuilder, IReadOnlyList<Property> dependentProperties, Key principalKey, string navigationToPrincipalName, Nullable<bool> isRequired, Nullable<ConfigurationSource> configurationSource)
Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.CreateForeignKey(InternalEntityTypeBuilder principalEntityTypeBuilder, IReadOnlyList<Property> dependentProperties, Key principalKey, string navigationToPrincipalName, Nullable<bool> isRequired, ConfigurationSource configurationSource)
Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.HasRelationship(EntityType targetEntityType, Nullable<MemberIdentity> navigationToTarget, Nullable<MemberIdentity> inverseNavigation, bool setTargetAsPrincipal, ConfigurationSource configurationSource, Nullable<bool> required)
Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.HasRelationship(EntityType targetEntityType, MemberInfo navigationProperty, ConfigurationSource configurationSource, bool setTargetAsPrincipal)
Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder<TEntity>.HasOne<TRelatedEntity>(Expression<Func<TEntity, TRelatedEntity>> navigationExpression)
Hl7Map.Infrastructure.SqlServer.NgoaiTru.NgoaiTruContext+<>c.<OnModelCreating>b__322_31(EntityTypeBuilder<MauYdcChiTiet> entity) in NgoaiTruContext.cs
+
                entity.HasOne(d => d.IdphieuNavigation)
Microsoft.EntityFrameworkCore.ModelBuilder.Entity<TEntity>(Action<EntityTypeBuilder<TEntity>> buildAction)
Hl7Map.Infrastructure.SqlServer.NgoaiTru.NgoaiTruContext.OnModelCreating(ModelBuilder modelBuilder) in NgoaiTruContext.cs
+
            modelBuilder.Entity<MauYdcChiTiet>(entity =>
Microsoft.EntityFrameworkCore.Infrastructure.ModelCustomizer.Customize(ModelBuilder modelBuilder, DbContext context)
Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.CreateModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.GetModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
Microsoft.EntityFrameworkCore.Internal.DbContextServices.CreateModel()
Microsoft.EntityFrameworkCore.Internal.DbContextServices.get_Model()
Microsoft.EntityFrameworkCore.Infrastructure.EntityFrameworkServicesBuilder+<>c.<TryAddCoreServices>b__7_3(IServiceProvider p)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSite(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSite(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine+<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService<T>(IServiceProvider provider)
Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
Microsoft.EntityFrameworkCore.DbContext.get_Model()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityType()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.CheckState()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityQueryable()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.System.Linq.IQueryable.get_Provider()
System.Linq.Queryable.Where<TSource>(IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
Hl7Map.Manager.Administration.PatientManager.Get(string IdBenhNhan) in PatientManager.cs
+
            var tttn= _myContext.MyOtherTable.Where(ttTiepnhan => ttTiepnhan.MaBn == IdBenhNhan)?.FirstOrDefault();
Hl7Map.Areas.FHIR.Controllers.PatientsController.Get(string idBn) in PatientsController.cs
+
            var pt = await _patientManager.Get(idBn);
lambda_method(Closure , object )
Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable+Awaiter.GetResult()
Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor+AwaitableObjectResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, object controller, object[] arguments)
System.Threading.Tasks.ValueTask<TResult>.get_Result()
System.Runtime.CompilerServices.ValueTaskAwaiter<TResult>.GetResult()
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask<IActionResult> actionResultValueTask)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

I already use lazy loading for EF Core:

services.AddDbContext<MyContext>(options =>
                options.UseLazyLoadingProxies().UseSqlServer(config.GetConnectionString("MyConnectionString"))
            );

Debug shows the program stuck while running Context constructor and entity builder ==> so it didn't even reach the Where() expression, so add ? after Where(..) won't fix.

What is the problem with EF Core? I'm stuck for this so long.

Why are they generated as HasNoKey? I'm not sure if the constraints are violated in your case, but generally, the relations between "normal" entities and keyless entities are restricted, so the statement entity.HasOne(d => d.IdphieuNavigation).WithMany()... looks specially suspicious to me — grek40
– grek40, Commented Aug 26, 2020 at 6:44
@grek40 Because the database builder didnt set primary key for the table (maybe for speed add/modify data), which leaves me with the current database => change the whole database set up would be exhausting, so I wouldnt think about it now. However the principal key is identity so it should be unique. The problem with me now is how to use EF Core to work with the current set up. I may revert to use ADO. net but I really want to avoid that — Duc Dang
– Duc Dang, Commented Aug 26, 2020 at 7:25
First time I see a Decimal type used as ID. Maybe changing it to integer would work? — Just Shadow
– Just Shadow, Commented Aug 26, 2020 at 7:49
@JustShadow Yeah it's really strange such settings. But like I said above, I can hardly do anything about it, cause it would cause problems in many other works. Really wish to have it worked with Entity Framework — Duc Dang
– Duc Dang, Commented Aug 26, 2020 at 8:21
If this is a one-time process, you can manually change the generated model + code (change decimal to long and the relevant property definitions to key definitions). But if you plan to redo the database-to-code transfer in the future, this might be a bad idea. When I worked on a code first from database project in EF6, the generated model always had some minor faults that need to be corrected before moving on. — grek40
– grek40, Commented Aug 28, 2020 at 6:00

Dharman · Accepted Answer · 2020-09-04 08:16:08Z

2

After trying to make it work with the existing database => and fail, the only solution is add key to both tables (principal and referencing tables) for EF Core to function properly. EF does not allow for foreign key constraints on no key tables.

edited Sep 4, 2020 at 8:16

Dharman♦

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answered Sep 4, 2020 at 3:06

Duc Dang

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Comments

Gilberto Alexandre · Accepted Answer · 2020-10-06 16:41:38Z

2

Complementing the answer ...

In practice, this error occurs because the entity was defined as "No key"

So, when the context is initialized, it generates error when defining the relationship ...

That HasNoKey was included by the scaffold process, because it did not identify a Primary Key field within my 'Departamento' table

answered Oct 6, 2020 at 16:41

Gilberto Alexandre

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