How to track Many-to-Many fields? (EFCore)

[J3ster1337]

I'm trying to make auditing work for many-to-many relationship for my tables, however, it isn't working
Here is my code:
Classes:

public class Client
    {
        public int Id { get; set; }
        public ICollection<ReportagePhoto>? ChosenPortraitPhotos { get; set; }
        public string? ParentName { get; set; }
        public string? ParentNumber { get; set; }
    }
    public class PortraitPhoto 
    {
        public int Id { get; set; }
        public byte[] Previev { get; set; }
        public ICollection<Client>? PeopleWhoSelectedIt { get; set; }
    } 

They are connected via Fluent API:

    modelBuilder.Entity<Client>()
                            .HasMany(c => c.ChosenPortraitPhotos)
                            .WithMany(s => s.PeopleWhoSelectedIt)
                            .UsingEntity<Dictionary<string, object>>(
                                  "ClientChosenPortraitPhotos",
                                  j => j.HasOne<PortraitPhoto>().WithMany().OnDelete(DeleteBehavior.NoAction),
                                  j => j.HasOne<Client>().WithMany().OnDelete(DeleteBehavior.NoAction));

Audit Class code:

    public class ClientChangeHistoryAudit
    {
        [Key] public int AuditId { get; set; }
        public int ClientId { get; set; }
        public string? ChangedPropertyName { get; set; }
        public string? OldValue { get; set; }
    }

In OnModelCreating I have this (take a note that IncludeAny(t => t.Name.StartsWith("Client")) includes fluent-api-coded "ClientChosenPortraitPhotos" table)

Audit.EntityFramework.Configuration.Setup()
                         .ForContext<ApplicationDbContext>(config => config
                         .IncludeEntityObjects()
                         .AuditEventType("Update"))
                         .UseOptIn()
                         .IncludeAny(t => t.Name.StartsWith("Client"));
            Audit.Core.Configuration.Setup()
                                    .UseEntityFramework(ef => ef
                                    .AuditTypeExplicitMapper(map => map
                                    .Map<Client, ClientChangeHistoryAudit>()
                .AuditEntityAction<ClientChangeHistoryAudit>((evt, entry, auditEntity) =>
                {
                    auditEntity.ClientId = (int)entry.PrimaryKey.First().Value;
                    if (entry.Changes != null)
                    {
                        foreach (var change in entry.Changes)
                        {
                            System.Diagnostics.Debug.WriteLine(change.ColumnName);
                            auditEntity.ChangedPropertyName = change.ColumnName;
                            if (change.ColumnName == "ParentName" || change.ColumnName == "ParentNumber")
                                auditEntity.OldValue = change.OriginalValue?.ToString();
                            if (change.ColumnName == "ChosenPortraitPhotos")
                            {
                                foreach (var photoChange in ((dynamic)change).OriginalValue.ToList())
                                    ((dynamic)auditEntity).OldValue += photoChange.Id.ToString() + " ";
                            }
                        }
                    }
                })));

I use System.Diagnostics.Debug.WriteLine(change.ColumnName); in it, so it should print name of every changed variable in table "Client" and "ClientChosenPortraitPhotos".
And it should store every change, with its column name and previous value in "ClientChangeHistoryAudit" table

However, when i'm executing that code

//setup for TestClient1, TestPortrait2, and other, saved with SaveChanges()
TestClient1.ChosenPortraitPhotos = new List<PortraitPhoto> { TestPortrait2 };
context.SaveChanges();
TestClient1.ParentName = "LOL";
context.SaveChanges();
TestClient1.ParentNumber = "123";
context.SaveChanges();

My Output gives me only:

"ParentName
ParentNumber"

And so, no changes for ChosenPortraitPhotos goes into the audit table.
What do I need to do to track them?

[thepirat000]

please check https://github.com/thepirat000/Audit.NET/blob/master/src/Audit.EntityFramework/README.md#map-many-to-many-relations-without-join-entity

[J3ster1337]

@thepirat000, Thank you for the reply, I've tried it, but this code now just don't create any audit logs at all.

Audit.Core.Configuration.Setup()
           .UseEntityFramework(ef => ef
           .AuditTypeExplicitMapper(map => map
           .MapTable<ClientChangeHistoryAudit>("ClientChangeHistoryAudit", (EventEntry ent, ClientChangeHistoryAudit audit) =>
           {
                     audit.ClientId = (int)ent.ColumnValues["PeopleWhoSelectedIt"];
                     audit.PhotoId = (int)ent.ColumnValues["ChosenPortraitPhotos"]; 
           })
          .AuditEntityAction<ClientChangeHistoryAudit>((evt, entry, auditEntity) =>
          {
              auditEntity.ChangeTime = DateTime.UtcNow;
              auditEntity.AuditAction = entry.Action;
          })));

And this too

    public class ClientChangeHistoryAudit
    {
        [Key] public int AuditId { get; set; }
        public Client? Client { get; set; }
        public PortraitPhoto? Photo { get; set; }
        //other
   }

  .MapTable<ClientChangeHistoryAudit>("ClientChangeHistoryAudit", (EventEntry ent, ClientChangeHistoryAudit audit) =>
  {
    audit.Client = (Client)ent.ColumnValues["PeopleWhoSelectedIt"];
    audit.Photo = (PortraitPhoto)ent.ColumnValues["ChosenPortraitPhotos"];
  })

[thepirat000]

Note that the first parameter of the .MapTable<AuditType>("AuditedTableName", ...) call must be the table name of the relation table you want to audit, and NOT the audit table, so your code should look like this:

 .MapTable<ClientChangeHistoryAudit>("ClientChosenPortraitPhotos", ...)

[J3ster1337]

@thepirat000 Thanks a lot! Now it all works as intended (but actually not as I initially imagined, I'm still acclimating to databases after OOP)

I will drop my code here in case someone will need it later (look! it's MANY many-to-many relationships!):

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
      base.OnModelCreating(modelBuilder);
      Audit.Core.Configuration.Setup()
                           .UseEntityFramework(ef => ef
                           .AuditTypeExplicitMapper(map => map
                               .MapTable("ClientChosenPortraitPhotos", (EventEntry ent, ClientChangeHistoryAudit audit) =>
                               {
                                    audit.ClientId = (int)ent.ColumnValues["PeopleWhoSelectedItId"];
                                    audit.PhotoId = (int)ent.ColumnValues["ChosenPortraitPhotosId"];
                                    audit.ChangedFieldName = "ChosenPortraitPhotos";
                               })
                               .MapTable("ClientChosenReportagePhotos", (EventEntry ent, ClientChangeHistoryAudit audit) =>
                               {
                                    audit.ClientId = (int)ent.ColumnValues["PeopleWhoSelectedItId"];
                                    audit.PhotoId = (int)ent.ColumnValues["ChosenReportagePhotosId"];
                                    audit.ChangedFieldName = "ChosenReportagePhotos";
                               })
                            .AuditEntityAction<ClientChangeHistoryAudit>((evt, entry, auditEntity) =>
                            {
                                auditEntity.ChangeTime = DateTime.UtcNow;
                                auditEntity.Action = entry.Action;
                            })));

        modelBuilder.Entity<Client>()
                    .HasMany(c => c.ChosenPortraitPhotos)
                    .WithMany(s => s.PeopleWhoSelectedIt)
                    .UsingEntity<Dictionary<string, object>>(
                          "ClientChosenPortraitPhotos",
                          j => j.HasOne<PortraitPhoto>().WithMany().OnDelete(DeleteBehavior.NoAction),
                          j => j.HasOne<Client>().WithMany().OnDelete(DeleteBehavior.NoAction));
        modelBuilder.Entity<Client>()
                    .HasMany(c => c.ChosenReportagePhotos)
                    .WithMany(s => s.PeopleWhoSelectedIt)
                    .UsingEntity<Dictionary<string, object>>(
                          "ClientChosenReportagePhotos",
                          j => j.HasOne<ReportagePhoto>().WithMany().OnDelete(DeleteBehavior.NoAction),
                          j => j.HasOne<Client>().WithMany().OnDelete(DeleteBehavior.NoAction));