Entity Framework 6 (code first) entity versioning and auditing

c# entity-framework entity-framework-6 sql-server


I'm looking at using Entity Framework 6.1.1 with SQL Server 2008 R2.

Currently I'm creating my models and database using the code-first EF feature. My basic use-case is to create a journal of all changes to a particular entity (ID is the key column) to help auditors track all changes made and by whom. e.g:

|ID|Version|Created Date|Created By|Modified Date|Modified By|Modify Action| ... (rest of entity fields)
| 4| 12    | 12-Mar-14  | tom      | 20-Feb-15   | jack      | Update      |
| 4| 11    | 12-Mar-14  | tom      | 14-Feb-15   | jill      | Update      |
| 4| 1     | 12-Mar-14  | tom      | 12-Mar-14   | tom       | Create      |

Does Entity Framework support this type of database scheme? If so, how can I set my models/solution up to facilitate this?

The other alternative I have is by intercepting all calls to the SaveChanges() method on the DbContext and log all database changes into a separate Audit table, but this might make retrieving information more challenging.

Any help on creating audit trails with SQL Server and EF 6 would be greately appreciated.

2/20/2015 11:19:07 AM

Popular Answer

I have used the 2nd approach you mention, by overloading the dbContext SaveChanges() method:

public class MyContext : DbContext

 public int SaveChanges(int userId)
    // Get all Added/Deleted/Modified entities (not Unmodified or Detached)
    foreach (var ent in this.ChangeTracker.Entries().Where(p => p.State ==  EntityState.Added 
    || p.State == EntityState.Deleted || p.State == EntityState.Modified))

        foreach (AuditLog x in GetAuditRecordsForChange(ent, userId))
    return base.SaveChanges();

So if I want to log a particular entity, I just call the overloaded SaveChanges & pass in a UserId:

public void Update(StockCatalogueItem entity, int userId)

I also have a custom DoNotLog attribute which I use to decorate the entity properties that I don't want to log. Without this, the logging could generate a huge amount of data, as each entity modification equals one db entry.

public int CreatedBy { get; set; }

The GetAuditRecordsForChange method does the checking for any DoNotLog properties and returns a List<AuditLog> which gets saved in the AuditLogs table:

public class AuditLog
        public int Id { get; set; }
        public int CreatedBy { get; set; }
        public DateTime CreatedOn { get; set; }
        public AuditEventType EventType { get; set; }
        public string TableName { get; set; }
        public int EntityId { get; set; }
        public string ColumnName { get; set; }
        public string Controller { get; set; }
        public string Action { get; set; }
        public string IPAddress { get; set; }
        public string OriginalValue { get; set; }
        public string NewValue { get; set; }
2/20/2015 11:46:32 AM

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