CODEWITHSUNDEEP
entity-frameworkentity-framework-4.1
DDiVita
DDiVita

Reputation: 4265

Auditing many-to-many relationships in Entity Framework?

I have been reading some artices about using the RelationshipManager to gain access to the entries that have related data. It is still unclear to me what the best way to audit when an entity whose related data is added or updated.

Sample Classes:

public class Rfi
{
     public Guid Id {get;set;}
     public string Number {get;set;}
     public virtual ICollection<Attachment> Attachments {get;set;}
}

public Class Attachment
{
    public Guid Id {get;set;}
    public string Name {get;set;}
    public string Description {get;set;}
    public string FileName {get;set;}
    public string Path {get;set;}        
}

Sample Mappings:

public class RfiMapping: EntityTypeConfiguration<Rfi>
{
     public Rfimapping()
     {
        HasMany(r => r.Attachments).WithMany().Map(m =>
                                                           {
                                                               m.MapLeftKey("RfiId");
                                                               m.MapRightKey("AttachmentId");
                                                               m.ToTable("Rfi_Attachments");
                                                           });
     }
}

I am using the Repository and Unit Of Work patterns. My UoW inherits from DbContext. A repository call may look like this:

public void AddAttachmentToRfi(Attachment attachment, Guid rfiId)
{
     var rfi = _rfiRepository.FindById(rfiId);
     rfi.Attachments.Add(attachment);
     _rfiRepository.UnitOfWork.Commit();
}

Is it possible , in an overridden SaveChanges method, to figure out that an Attachment entity was added to an Rfi entity? When I traverse the, say ChangeTracker.Entries, I am not seeing its state being set to modified. Which makes sense, because I am only adding to the relationships and not the entity directly.

I know to cast my DbContext to an IObjectContextAdapter, but I am not sure what I need to do with the RelationshipManager to get the changes made to any of the relationships. I am also curious to know if I were to update an Attachment's Description property later on, if I can still see what changes were made to any related data.

My goal with this is, the user interface for the Rfi allows users to attach files (Rfi is obviously not the only entity that can have attachments). I need to show a history of everything that happens to an Rfi. This means if an attachment is added I need to audit it. If the attachment's data is updated, I need to audit those changes and show that they were updated via the Rfi interface. This may get complicated if that attachment is shared with another entity, but I will cross that road later.

Upvotes: 3

Views: 997

Answers (1)

Shiraz Bhaiji
Shiraz Bhaiji

Reputation: 65491

As you say you are not changing any of the entities only the relationship between them.

EF will then convert this to an insert into or delete from the Rfi_Attachments table.

One way to audit this is to add a database trigger that writes an entry to a log table, each time an entry is added or deleted.

Upvotes: 1

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