Entity Framework CORE Seeding Joining table

Question

I am working on .NET CORE 6 along with EF CORE 7. I need to seed data in joining table but unable to do so and get error.

I am seed FileTypeId but not sure why EF core migration throwing error...

error

The seed entity for entity type 'JobFileType' cannot be added because it has the navigation 'FileType' set. To seed relationships,  add the entity seed to 'JobFileType' and specify the foreign key values {'FileTypeId'}. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the involved property values.

ClassA

public class JobProfile
{
    public JobProfile()
    {
        this.JobFileTypes = new HashSet<JobFileType>();
    }

    public Guid JobProfileId { get; set; }
    public string Name { get; set; }
    public ICollection<JobFileType>? JobFileTypes { get; set; }
}

ClassB

public class FileType
{
    public FileType()
    {
        this.JobFileTypes = new HashSet<JobFileType>();
    }

    public Guid FileTypeId { get; set; }
    public string Extension { get; set; } = string.Empty;
    public ICollection<JobFileType>? JobFileTypes { get; set; }
}

Joing Table

 public class JobFileType
{
    public Guid JobFileTypeId { get; set; }
    public Guid JobProfileId { get; set; }
    public JobProfile JobProfile { get; set; } = new JobProfile();
    public Guid FileTypeId { get; set; }
    public FileType FileType { get; set; } = new FileType();
}

Seed Extension

public static class JobFileTypeSeed
{
    public static void Seed(this ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<JobFileType>()
            .HasData(
                new JobFileType {JobFileTypeId = Guid.Parse("aaa"), JobProfileId = Guid.Parse("ccc"), FileTypeId = Guid.Parse("yyy") },
                new JobFileType { JobFileTypeId = Guid.Parse("bbb"), JobProfileId = Guid.Parse("ccc"), FileTypeId = Guid.Parse("zzz") }
              );
    }
}

config

internal class JobFileTypeConfiguration : IEntityTypeConfiguration<JobFileType>
{
    public void Configure(EntityTypeBuilder<JobFileType> builder)
    {
        builder.ToTable("JobFileType", "dbo");

        builder.HasKey(column => column.JobFileTypeId);

        builder
            .HasOne(jobFileType => jobFileType.JobProfile)
            .WithMany(jobProfile => jobProfile.JobFileTypes)
            .HasForeignKey(jobFileType => jobFileType.JobProfileId);

        builder
            .HasOne(jobFileType => jobFileType.FileType)
            .WithMany(fileType => fileType.JobFileTypes)
            .HasForeignKey(jobFileType => jobFileType.FileTypeId);
       
    }
}

Answer 1

There is not much to say about the concrete issue (which btw is not specific to joining entity, but any entity model seeding):

I am seed FileTypeId but not sure why EF core migration throwing error...

as the cause of the issue is included at the beginning of the error message:

because it has the navigation 'FileType' set.

And your entity has

public FileType FileType { get; set; } = new FileType();
//                                     ^  ^   ^
//                                     the problem

and the same for

public JobProfile JobProfile { get; set; } = new JobProfile();

which will be the next error if you resolve the original.

Remove both navigation property initializers (= new ...) and the problem will be gone.

As a general rule, you should never initialize reference navigation properties because it causes many side effects and/or improper behaviors (not only for seeding, but also eager/lazy/explicit data loading). Initializing collection navigation properties is arbitrary, but ok. Only reference navigation property initialization must be avoided. For more info, see EF codefirst : Should I initialize navigation properties? - quite old EF topic, but still applies.

If you are trying to resolve NRT warnings (as I guess), initializing with new is definitely not a proper way. One reason I don't like NRT is because it is forcing people to use "workarounds" for preventing compiler warnings, which in fact break the primary functionality. Specifically in EF Core, enabling NRT also changes the optional/required attribute of some properties, hence database column types (most noticeable for string properties/columns and reference navigations). You could read more about this in the Working with Nullable Reference Types topic in the official EF Core documentation, but in general I would just disable NRT for EF entity model classes.

Answer 2

The proper order is to set the "master data" first and then try to set the join table, as you would expect.

The defaulting

{get;set;} = new Something();

Could be the offending declaration, since any instance upon creation will have the relation JobFileType already set