Auditing many-to-many relationships in Entity Framework?
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;}
}

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

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