EF Core 6 Unable to set up a many-to-many relationship between '' and '' because one or both of the navigations don't have a corresponding CLR property

[ngoov]

I am using a many to many relation in my app that has a navigation property (collection) only on 1 side and using a join table.
After updating the nuget packages of EF Core to 6.0.0 from 5.0.12, I am receiving this error when I am trying to add a new migration using dotnet ef migrations add test.

I have reproduced my problem in this small console app written in .NET 6:

// See https://aka.ms/new-console-template for more information
using Microsoft.EntityFrameworkCore;

Console.WriteLine("Hello, World!");

public class Context : DbContext
{
    public DbSet<Client> Clients { get; set; }

    public string DbPath { get; private set; }

    public Context()
    {
        var folder = Environment.SpecialFolder.LocalApplicationData;
        var path = Environment.GetFolderPath(folder);
        DbPath = $"{path}{System.IO.Path.DirectorySeparatorChar}context.db";
    }

    // The following configures EF to create a Sqlite database file in the
    // special "local" folder for your platform.
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlite($"Data Source={DbPath}");

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<Client>().HasMany(x => x.Claims).WithMany("Clients").UsingEntity<ClientClaim>(
            e => e.HasOne(x => x.Claim).WithMany(),
            e => e.HasOne(x => x.Client).WithMany(),
            join =>
            {
                join.ToTable("clients_claims");
                join.HasKey($"{nameof(Client)}Id", $"{nameof(Claim)}Id");
            });
    }
}

public class Client
{
    public Guid Id { get; set; }
    public ICollection<Claim> Claims { get; set; }
}

public class Claim
{
    public Guid Id { get; set; }
}

public class ClientClaim
{
    public Client Client { get; set; }
    public Claim Claim { get; set; }
}

Using the EF Core 5.0.12 packages, the output is as expected and the migration is created:

$ dotnet ef migrations add initial
Build started...
Build succeeded.
Done. To undo this action, use 'ef migrations remove'

When I update the EF Core nuget packages to 6.0.0, the following error is thrown (I have removed some file paths in the output for privacy reasons):

dotnet ef migrations add initial --verbose
Using project '\EFCore6ManyToMany.csproj'.
Using startup project '\EFCore6ManyToMany.csproj'.
Writing '\obj\EFCore6ManyToMany.csproj.EntityFrameworkCore.targets'...
dotnet msbuild /target:GetEFProjectMetadata /property:EFProjectMetadataFile=\tmpEE8D.tmp /verbosity:quiet /nologo \EFCore6ManyToMany.csproj
Writing '\obj\EFCore6ManyToMany.csproj.EntityFrameworkCore.targets'...
dotnet msbuild /target:GetEFProjectMetadata /property:EFProjectMetadataFile=\tmpF0A1.tmp /verbosity:quiet /nologo \EFCore6ManyToMany.csproj
Build started...
dotnet build \EFCore6ManyToMany.csproj /verbosity:quiet /nologo
\Program.cs(51,19): warning CS8618: Non-nullable property 'Client' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(52,18): warning CS8618: Non-nullable property 'Claim' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(41,31): warning CS8618: Non-nullable property 'Claims' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(12,12): warning CS8618: Non-nullable property 'Clients' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]

Build succeeded.

\Program.cs(51,19): warning CS8618: Non-nullable property 'Client' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(52,18): warning CS8618: Non-nullable property 'Claim' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(41,31): warning CS8618: Non-nullable property 'Claims' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
\Program.cs(12,12): warning CS8618: Non-nullable property 'Clients' must contain a non-null value when exiting constructor. Consider declaring the property as nullable. [\EFCore6ManyToMany.csproj]
    4 Warning(s)
    0 Error(s)

Time Elapsed 00:00:01.10
Build succeeded.
dotnet exec --depsfile \bin\Debug\net6.0\EFCore6ManyToMany.deps.json --additionalprobingpath C:\Users\ --additionalprobingpath "C:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages" --additionalprobingpath "C:\Program Files (x86)\Microsoft\Xamarin\NuGet" --additionalprobingpath "C:\Program Files\dotnet\sdk\NuGetFallbackFolder" --runtimeconfig \bin\Debug\net6.0\EFCore6ManyToMany.runtimeconfig.json C:\Users\\.store\dotnet-ef\6.0.0\dotnet-ef\6.0.0\tools\netcoreapp3.1\any\tools\netcoreapp2.0\any\ef.dll migrations add initial --assembly \bin\Debug\net6.0\EFCore6ManyToMany.dll --project \EFCore6ManyToMany.csproj --startup-assembly \bin\Debug\net6.0\EFCore6ManyToMany.dll --startup-project \EFCore6ManyToMany.csproj --project-dir \ --root-namespace EFCore6ManyToMany --language C# --framework net6.0 --nullable --working-dir  --verbose
Using assembly 'EFCore6ManyToMany'.
Using startup assembly 'EFCore6ManyToMany'.
Using application base '\bin\Debug\net6.0'.
Using working directory ''.
Using root namespace 'EFCore6ManyToMany'.
Using project directory '\'.
Remaining arguments: .
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider in assembly 'EFCore6ManyToMany'...
Finding Microsoft.Extensions.Hosting service provider...
No static method 'CreateHostBuilder(string[])' was found on class 'Program'.
No application service provider was found.
Finding DbContext classes in the project...
Found DbContext 'Context'.
Using context 'Context'.
System.InvalidOperationException: Unable to set up a many-to-many relationship between 'Claim.Clients' and 'Client.Claims' because one or both of the navigations don't have a corresponding CLR property. Consider adding a corresponding private property to the entity CLR type.
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelValidator.ValidateRelationships(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.Sqlite.Infrastructure.Internal.SqliteModelValidator.Validate(IModel model, IDiagnosticsLogger`1 logger)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelRuntimeInitializer.Initialize(IModel model, Boolean designTime, IDiagnosticsLogger`1 validationLogger)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.GetModel(DbContext context, ModelCreationDependencies modelCreationDependencies, Boolean designTime)
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.CreateModel(Boolean designTime)
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.get_Model()
   at Microsoft.EntityFrameworkCore.Infrastructure.EntityFrameworkServicesBuilder.<>c.<TryAddCoreServices>b__8_4(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 callSite, 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 callSite, 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 callSite, 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 callSite, 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 callSite, 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 callSite, 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__DisplayClass2_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.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_ContextServices()
   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.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to set up a many-to-many relationship between 'Claim.Clients' and 'Client.Claims' because one or both of the navigations don't have a corresponding CLR property. Consider adding a corresponding private property to the entity CLR type.

EF Core version: 6.0.0
Database provider: Any. This test app uses sqlite, my own project uses npgsql and mssqlserver
Target framework: .NET 6
Operating system: Windows 10 Pro
IDE: Any, using command line tool

[ajcvickers]

@ngoov This is a duplicate of #23362. Unidirectional many-to-many relationships (tracked by #3864) are not supported. However, the workaround is easy: create a private navigation property for the inverse. See #3864 (comment).

[ngoov]

@ajcvickers Thanks for the reply. I will try it with the workaround.
Any idea though why it was working as expected in EF Core 5?

[ajcvickers]

@ngoov It wasn't really working; but we didn't validate the input and some things worked. So, depending what you did with the relationship, it would work, but not reliably.

[ngoov]

@ajcvickers Ok, thanks for the explanation. In the meanwhile, I can confirm that the workaround is working as expected, so I'll close this issue.
I will follow #3864 and hope it is coming to EF Core 7!