Asp.net – Entity's primary key not being updated after changes are saved

I have a DDD setup in C#, linking entities to DB tables. An entity has a configured Id (primary key) that encapsulates a non-negative, non-zero integer (a value object). I have the primary key configured in EF Core fluent API, and have configured a converter for the primary key property to convert to/from int. On the DB side (MySQL) the primary key is an auto-incrementing int.

When I create a new entity instance, a new row is added to the table with an Id value I would expect. However, on the EF Core side, the added entity does not have an Id matching the Id in the DB.

I am using CSharpFunctionalExtensions (https://github.com/vkhorikov/CSharpFunctionalExtensions) for the value objects.

My entities look like this:

public class Entity
{
    Entity() {}
    
    public static Entity CreateNew() 
    {
        Id = EntityId.CreateNew();
    }

    public EntityId Id { get; private init; } = null;
    ...
}

My entity ids look like this:

public class EntityId : SimpleValueObject<int>
{
    EntityId(int value)  : base(value) {}
    
    public static EntityId CreateNew() 
    {
        return new EntityId(0);
    }
}

SimpleValueObject wraps a Type T and just provides some comparison and equality overloads

public T Value { get; private set; }

My MySQL table is as follows:

CREATE TABLE entity
(
    EntityId INT            NOT NULL AUTO_INCREMENT PRIMARY KEY,
    Field1 NVARCHAR(3072) NOT NULL,
    Field2 INT            NOT NULL,
    ...
);

The entity is configured in EF Core as follows:

public class EntityConfiguration : IEntityTypeConfiguration<Entity>
{
    public void Configure(EntityTypeBuilder<Entity> builder)
    {
        builder.ToTable("entity");

        builder.HasKey(j => j.Id).HasName("PRIMARY");

        builder
            .Property(e => e.Id)
            .HasConversion(v => v.Value, v => EntityId.Create(v).Value)
            .HasColumnName("EntityId")
            .HasColumnType("int(11)");
    }
}

When I run the following code, the entity’s Id does not update to match what is saved, but remains 0:

var entity = Entity.CreateNew();
_db.Entities.Add(entity);

await _db.SaveChangesAsync(cancellationToken);

// Expect Id to be the auto-generated value
var id = entity.Id; // But, this returns an EntityId with Value = 0

var allEntities = _db.Entities; // However, the entity has the correct Id value in the dbcontext

I have been agonizing over this for a day now. Any advice or suggestions are appreciated.

I have tried configuring the EF Core setup multiple different ways. I’ve tried backing fields and ValueGeneratedOnAdd. The only thing that has worked is removing the EntityId object and replacing it with an int. Then the Id value is updated when the entity is saved. But I don’t know why the same doesn’t work for a field represented by a Value Object.

Edit: I have tried

ValueGeneratedOnAdd()

using EF Core’s fluent API, but that didn’t work either.

EDIT: Runtimes

• EF Core v8.0.8
• .NET v8.0.303