Update .NET Microservices infrastructure docs

[amyboose]

After using navigation properties in many-to-many relationship I've got exceptions on every entity with navigation property. But it works well after comments code lines with navigation set.

public class TestContext : DbContext
{

        private readonly string _connectionString;
        public TestContext(string connectionString)
        {
            _connectionString = connectionString;
        }

        public DbSet<User> Users { get; private set; }
        public DbSet<Blog> Blogs { get; private set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(_connectionString,
                o => o.UseQuerySplittingBehavior(QuerySplittingBehavior.SplitQuery));
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new UserConfiguration());
            modelBuilder.ApplyConfiguration(new BlogConfiguration());
        }
    }

    public class User
    {
        private readonly List<Blog> _blogCollection = new();

        public int Id { get; set; }
        public IReadOnlyCollection<Blog> BlogCollection => _blogCollection.AsReadOnly();
    }

    public class Blog
    {
        private readonly List<User> _userCollection = new();

        public int Id { get; set; }
        public IReadOnlyCollection<User> UserCollection => _userCollection.AsReadOnly();
    }

    internal class UserConfiguration : IEntityTypeConfiguration<User>
    {
        public void Configure(EntityTypeBuilder<User> builder)
        {
            var navigation = builder.Metadata.FindNavigation(nameof(User.BlogCollection));
            navigation.SetPropertyAccessMode(PropertyAccessMode.Field);

            builder.HasMany(p => p.BlogCollection)
                .WithMany(p => p.UserCollection)
                .UsingEntity(j => j.ToTable("MayToManyTableName"));
        }
    }

    internal class BlogConfiguration : IEntityTypeConfiguration<Blog>
    {
        public void Configure(EntityTypeBuilder<Blog> builder)
        {
            var navigation = builder.Metadata.FindNavigation(nameof(Blog.UserCollection));
            navigation.SetPropertyAccessMode(PropertyAccessMode.Field);
        }
    }

[ajcvickers]

@amyboose Please post the code that uses the entities, and the exceptions and stack traces you are seeing.

[amyboose]

@amyboose Please post the code that uses the entities, and the exceptions and stack traces you are seeing.

My exception after using command "add-migration init":

PM> add-migration init Build started... Build succeeded. System.NullReferenceException: Object reference not set to an instance of an object. at TestEfCoreManyToMany.UserConfiguration.Configure(EntityTypeBuilder1 builder) in C:\Users\Александр\source\repos\TestEfCoreManyToMany\TestEfCoreManyToMany\UserConfiguration.cs:line 57 at Microsoft.EntityFrameworkCore.ModelBuilder.ApplyConfiguration[TEntity](IEntityTypeConfiguration1 configuration) at TestEfCoreManyToMany.TestContext.OnModelCreating(ModelBuilder modelBuilder) in C:\Users\Александр\source\repos\TestEfCoreManyToMany\TestEfCoreManyToMany\UserConfiguration.cs:line 31 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, 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.b8_4(IServiceProvider p) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.VisitCallSite(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.VisitCallSite(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.VisitCallSite(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.VisitCallSite(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.VisitCallSite(ServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.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.CallSiteVisitor2.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.b0(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.get_Instance() at Microsoft.EntityFrameworkCore.Infrastructure.Internal.InfrastructureExtensions.GetService[TService](IInfrastructure1 accessor) at Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure1 accessor) at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func1 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_01.b__0() at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action) Object reference not set to an instance of an object. PM>

My code is practically the same. Difference just in connectionString:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;

namespace TestEfCoreManyToMany
{
    internal class TestContext : DbContext
    {
        private readonly string _connectionString;

        public TestContext()
        {
            _connectionString = @"data source=(localdb)\MSSQLLocalDB;Initial Catalog=ManyToManyTable;Integrated Security=True;";
        }

        public DbSet<User> Users { get; private set; }
        public DbSet<Blog> Blogs { get; private set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(_connectionString,
                o => o.UseQuerySplittingBehavior(QuerySplittingBehavior.SplitQuery));
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new UserConfiguration());
            modelBuilder.ApplyConfiguration(new BlogConfiguration());
        }
    }

    public class User
    {
        private readonly List<Blog> _blogCollection = new();

        public int Id { get; set; }
        public IReadOnlyCollection<Blog> BlogCollection => _blogCollection.AsReadOnly();
    }

    public class Blog
    {
        private readonly List<User> _userCollection = new();

        public int Id { get; set; }
        public IReadOnlyCollection<User> UserCollection => _userCollection.AsReadOnly();
    }

    internal class UserConfiguration : IEntityTypeConfiguration<User>
    {
        public void Configure(EntityTypeBuilder<User> builder)
        {
            var navigation = builder.Metadata.FindNavigation(nameof(User.BlogCollection));
            navigation.SetPropertyAccessMode(PropertyAccessMode.Field);

            builder.HasMany(p => p.BlogCollection)
                .WithMany(p => p.UserCollection)
                .UsingEntity(j => j.ToTable("MayToManyTableName"));
        }
    }

    internal class BlogConfiguration : IEntityTypeConfiguration<Blog>
    {
        public void Configure(EntityTypeBuilder<Blog> builder)
        {
            var navigation = builder.Metadata.FindNavigation(nameof(Blog.UserCollection));
            navigation.SetPropertyAccessMode(PropertyAccessMode.Field);
        }
    }
}

[ajcvickers]

@amyboose This piece of code should not be needed:

var navigation = builder.Metadata.FindNavigation(nameof(User.BlogCollection));
            navigation.SetPropertyAccessMode(PropertyAccessMode.Field);

What is the reason you have this code?

[amyboose]

I know that the the code works without navigation property. But in other cases navigation binding works well. Just many-to-many case throws an exception. This approach can confuse the user

[ajcvickers]

@amyboose FindNavigation won't work with many-to-many, but it should not be needed. What is the reason for using it here?

[amyboose]

I haven't an answer. Didn't check other cases where EF Core will search navigation for IReadonlyCollection. I just followed the advice of Microsoft documentation.

[ajcvickers]

@amyboose Can you point to the documentation you followed?

[amyboose]

https://docs.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/infrastructure-persistence-layer-implementation-entity-framework-core

[ajcvickers]

@amyboose That documentation is significantly out-of-date and doesn't cover current best practices or newer features like many-to-many relationships. I'm also not sure that the advice there is generally useful for most people using EF. We'll try to find the owner and see if it can be updated.

/cc @JeremyLikness

[amyboose]

Ok, thanks for answer