Use correct value comparers for collection properties with value conversion

My entity has a collection of SmartEnums (simplified in the code example below) which is persisted in the database using a ValueConverter in order to keep the domain model clean (I wanted to avoid introducing a wrapper entity with an extra ID property). It works correctly for retrieving data but unfortunately doesn’t seem to pick up changes to the collection automatically. When calling SaveChanges, the changes are not persisted unless the entity state is manually set to EntityState.Modified beforehand.

Steps to reproduce

MySmartEnum

public class MySmartEnum
    {
        public string Value { get; set; }

        public static MySmartEnum FromValue(string value)
        {
            return new MySmartEnum { Value = value };
        }
    }

Entity

public class Entity
    {
        public Entity()
        {
            SmartEnumCollection = new HashSet<MySmartEnum>();
        }

        public int Id { get; set; }
        public virtual ICollection<MySmartEnum> SmartEnumCollection { get; set; }
    }

Context

public class TestContext : DbContext
    {
        public TestContext()
        { }

        public TestContext(DbContextOptions<TestContext> options)
            : base(options)
        { }

        public virtual DbSet<Entity> Entities { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            var valueConverter = new ValueConverter<ICollection<MySmartEnum>, string>
            (
                e => string.Join(',', e.Select(c => c.Value)),
                str => new HashSet<MySmartEnum>(
                            str.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
                               .Select(x => MySmartEnum.FromValue(x)))
            );

            modelBuilder.Entity<Entity>()
                .Property(e => e.SmartEnumCollection)
                .HasConversion(valueConverter);
        }
    }

Update method

using (var context = new TestContext(options))
            {
                var entity = context.Entities
                    .First();

                entity.SmartEnumCollection.Add(MySmartEnum.FromValue("Test"));

                // Changes are persisted only if the following line is uncommented:
                //context.Entry(entity).State = EntityState.Modified;

                context.SaveChanges();
            }

Further technical details

EF Core version: 3.0.0-rc1.19427.8 Database Provider: Microsoft.EntityFrameworkCore.SqlServer (Version 3.0.0-rc1.19427.8) Operating system: Windows 10 (Version 10.0.18362.295) IDE: Visual Studio 2019 16.2.3