Entity Framework 4: Adding dervied entity won't show in count until save

Question

I have an "Investment" entity that is derived from "BaseEntity". If I create and add a new "Investment" like so:

investment = new Investment();
investment.Name = "Investment 01";
_context.BaseEntities.AddObject(entity);

and query the count (before saving changes)

_context.BaseEntities.OfType<Investment>().Count();

it returns zero. The same line returns 1 after _context.SaveChanges();

What am I doing wrong?

score 2 · Answer 1 · answered Apr 19 '11 at 11:18

2

You are not doing anything wrong. This is how EF works. No changes are done in database until you execute SaveChanges - it is called unit of work. You prepare all changes in memory and then save them all together in one transaction.

answered Apr 19 '11 at 11:18

Ladislav Mrnka

360,892
59
660
670

I now that. But my understanding is, that the DataContext should give me the right Count because it has new newly added object in memory. If I do: _container.BaseEntities.Count() I get the right number. – SolarX Apr 19 '11 at 11:22
I would like to have an ObjectSet of "Investment" rather than an "ObjectQuery". – SolarX Apr 19 '11 at 11:24

Alexandre Brisebois · Answer 2 · 2011-04-19T14:21:37.150

0

An entity which is still in insert state will not be included in query results since the object has not been persisted with the SaveChanges()

Executing the _context.BaseEntities.OfType<Investment>().Count(); method will make a request to the SQL server and return the results found in the database.

When using the GetObjectByKey method, a way to fetch the entity from the context instance if it was previously loaded,which is found on the ObjectContext, will also react the same way. Since the object is in new / insert state, the context will treat it as non existant until the save.

Edit:

In the code in the question you are using _context and in the comment you are mentioning _container.BaseEntities.Count()

what is the difference between these two objects ?

edited Apr 19 '11 at 14:21

answered Apr 19 '11 at 11:19

Alexandre Brisebois

6,599
12
50
69

So why can't I get an ObjectSet of "Investment"? I actually don't want to work with the ObjectQuery. – SolarX Apr 19 '11 at 11:28
why not work with an in-memory list and then commit to the context ? – Alexandre Brisebois Apr 19 '11 at 14:02
It would be possible to do that... But why bother. I can't understand why EF has to handle derived entities that different. – SolarX Apr 19 '11 at 14:09

score 0 · Answer 3 · answered Apr 19 '11 at 11:21

0

This is correct behavior as the object is sitting in the state manager until you call SaveChanges(). Only after you call SaveChanges() will the object become available in your count.

answered Apr 19 '11 at 11:21

Craig

6,869
3
32
52

Entity Framework 4: Adding dervied entity won't show in count until save

3 Answers3

Linked