Linq to SQL - Audit Trail (find old values in SubmitChanges)

Question

At the moment I'm looking for a way to find the old values of an entity in the [context].SubmitChanges().

As far as I can tell only the new values show up. Do I really need to do a query to the database to get the old values of the entity?

The solution by GertArnold:

    public override void SubmitChanges(System.Data.Linq.ConflictMode failureMode)
                {
                    // Get the changeset
                    ChangeSet changeSet = this.GetChangeSet();

                    // Put the updated objects into a IEnumerable
                    IEnumerable<object> updatedEntities = changeSet.Updates;

                    foreach (var entity in updatedEntities.Where(entity => AuditTypes.Contains(entity.GetType())))
                    {
                        var old = this.GetTable(entity.GetType()).GetModifiedMembers(entity);
                        // Do something with the old values
                    }

                    // Save the changes
                    base.SubmitChanges(failureMode);
                }

Answer 1

Looks like you're looking for the Table.GetModifiedMembers method.

As you want old values of an entity, this method is useful.