Entity Framework 5 : Proper method to replace entry in context

问题

What i want to do is simple. I have a list of parts in the db, and i want to delete/insert/update them according to an update list.

The main issue is that, when i want to replace an entry i can't attach it to the context because the older(to be updated) entry is already attached (by previous read call) and an exception is thrown.

I came around with 3 thoughts.

1. Manually Detach the old entry and attach the new one (although changing entity state to detached still throws exception)
2. Manually change the values of the old entry with the new ones
3. Make the read call non track able (AsNoTracking()), this seems to work fine but i am concerned about impact on lazyloading.

Is there any functionality like "context.entry.replace(oldEntry,newEntry)" or any other proper way to do this?

IEnumerable<SoldPart> old = db.SoldParts.Where(sp=>sp.sessionId == sessionId);

                var toDelete = old.Where(po=> !parts.Any(pu=>pu.id == po.id));
                var toCreate = parts.Where(po => !old.Any(pu => pu.id == po.id));
                var toUpdate = parts.Where(po => old.Any(pu => pu.id == po.id));


                foreach (SoldPart item in toDelete)
                {
                    db.SoldParts.Attach(item);
                    db.SoldParts.Remove(item);
                }
                foreach (SoldPart item in toCreate)
                {
                    db.SoldParts.Add(item);
                }

                foreach (SoldPart item in toUpdate)
                {

                    db.SoldParts.Attach(item);
                    db.Entry(item).State = EntityState.Modified;
                }


                db.SaveChanges();

回答1:

There is automatic way to update attached entity's values from detached one but it works only on scalar / complex properties. Not on navigation properties:

deb.Entry(oldEntry).CurrentValues.SetValues(newEntry);

来源：https://stackoverflow.com/questions/14471142/entity-framework-5-proper-method-to-replace-entry-in-context