UnitOfWork: Add + Delete in memory; then Save to DB fails
Joined: 14-Oct-2008
Joined: 14-Oct-2008
Hi,
-
The Runtime Library version = 2.6.8.911
-
The delete statements aren't there because everything happened in memory until the save. So I add a new AssessmentDamage in memory (who also holds 2 new AssessmentDamageChecks). Then I add a 2nd AssessmentDamage in memory (again with 2 new sub-entities). Then I remove the last AssessmentDamage added to memory, including its sub-entities. After all this, I try to save to the DataBase. Now an exception is thrown on the following line: vUnitOfWork.Commit(adapter, true); (the exception is visible in my first post)
I did another simple test, and this all works: Add 2 AssessmentDamages (including sub-entities) in memory. Do a save to the DataBase. (This works!!). Then delete the last AssessmentDamage added. (This also works !!). So it seems like the in memory deletion has something to do with it.
- Some more info about the 2nd AssessmentDamageCheck: I'm quite sure this assessmentDamageCheck gets added to the same collection. Look at my first post where I checked the HashCodes of these entities. The HashCode of the AssessmentDamage is the same as the 1st AssessmentDamageCheck's AssessmentDamage, and also the same as the 2nd AssessmentDamageCheck's AssessmentDamage. (Note: AssessmentDamageCheck.AssessmentDamages is an AssessmentDamage entity. It is in plural because my table name is plural (this could be confusing))
Also some code: Here I create my AssessmentDamageChecks. I just added a small part of the code to make it not too confusing. I iterate of this piece of code 2 times. During the iteration the entity View.Model.AssessmentDamage doesn't change so both AssessmentChecks that get created reference the same AssessmentDamage.
AssessmentDamageChecksEntity vAssessmentDamageChecksEntity = new AssessmentDamageChecksEntity()
{
AssessmentDamages = View.Model.AssessmentDamage,
MeasurePoints = vMeasurePointEntity,
Data = string.Empty
};
It seems like something weird is going on 
At your service to help or supply extra info ....
Kind regards, Wim
Joined: 14-Oct-2008
Joined: 14-Oct-2008
Joined: 14-Oct-2008
Joined: 14-Oct-2008
Hi Wim,
I think the problem is about deleting a parent while the children remains inside in the queue to save of the UnitOfWork. All is in the way you add the entities to the bucket. See this example of "how not proceed":
// Add stuff to UnitOfWork
UnitOfWork2 uow = new UnitOfWork2();
// Category 1 and children
uow.AddForSave(newCategory1);
uow.AddCollectionForSave(newCategory1.Products);
// Category 2 and children
uow.AddForSave(newCategory2);
uow.AddCollectionForSave(newCategory2.Products);
// Add for delte the Category 2
uow.AddForDelete(newCategory2);
// save entities
DataAccessAdapter adapter = new DataAccessAdapter();
uow.Commit(adapter);
Note that the _newCategory2 _is added (only the entity), then the newCategory2.Products are added. Then the _newCategory2 _is removed, that doesn't imply that the products collection are removed form the save queue. That will cause that the some products (children of newCategory2 will be persisted without the information (FK) of their category).
So, this is the same code modified a little bit no avoid the error:
// Add stuff to UnitOfWork
UnitOfWork2 uow = new UnitOfWork2();
// Category 1 (recursively)
uow.AddForSave(newCategory1, null, false, true);
// Category 2 (recursively)
uow.AddForSave(newCategory2, null, false, true);
// Add for delete the Category 2
uow.AddForDelete(newCategory2);
// save entities
DataAccessAdapter adapter = new DataAccessAdapter();
uow.Commit(adapter);
Above code will add newCategory2 recursively. So when you add it for delete, somehow the newCategory2 and it's products are removed from the save queue. No errors expected
I hope you can apply this concept to your project, otherwise please attach some repro (demo) zip we can build and recommend a solution.
Joined: 14-Oct-2008
Joined: 14-Oct-2008
hypo wrote:
Hi Daelmo,
thanks for your reply.
The solution you proposed doesn't work either, in fact our problem comes down to this: We have a entitycollection of parent object where each parent object has a entitycollection of child objects.
Wim, my point was that the error is due to the save of children whose parent have been removed from the save queue.
So, I'm pretty sure the problem is how you are removing entities from collections. If I'm not mistaken, this is your DELETE in-memory code:
private void btnDeleteAssessmentDamage_Click(object sender, RoutedEventArgs e)
{
EntityCollection<AssessmentDamagesEntity> vAssessmentDamages = GetSelectedAssessmentDamages();
for (int i = vAssessmentDamages.Count - 1; i >= 0; i--)
{
AssessmentDamagesEntity vAssessmentDamage = vAssessmentDamages[i];
for (int a = vAssessmentDamage.AssessmentDamageChecks.Count -1; a >= 0; a--)
{
//remove the assessmentDamageChecks
vAssessmentDamage.AssessmentDamageChecks.RemoveTracked(vAssessmentDamage.AssessmentDamageChecks[a]);
}
//remove the assessmentDamage
Model.AssessmentFile.AssessmentDamages.RemoveTracked(vAssessmentDamage);
}
Model.IsNew = true;
}
In that code, I see two weird things:
- You are removing (I think) entities from the collection you are iterating into. That is a little risky.
- What is the _RemoveTracked _method? Is that some custom code in the collection?
A repro solution would accelerate the resolution of this
Joined: 14-Oct-2008
daelmo wrote:
- You are removing (I think) entities from the collection you are iterating into. That is a little risky.
- What is the _RemoveTracked _method? Is that some custom code in the collection?
A repro solution would accelerate the resolution of this
Hi daelmo,
I know that I'm removing from the collection that I'm iterating through, that's why I use a for loop and iterate from the last to the first element.
This is our removeTracked (which is an extention method):
public static void RemoveTracked<TEntity>(this EntityCollection<TEntity> aEntityCollection, TEntity aObjectToRemove)
where TEntity : EntityBase2, IEntity2
{
if (aEntityCollection.RemovedEntitiesTracker == null)
{
aEntityCollection.RemovedEntitiesTracker = new EntityCollection<TEntity>();
}
aEntityCollection.Remove(aObjectToRemove);
}
The code might seem weird, but it all works perfectly when I'm adding and deleting entities normally. Only when I delete an entity which was added in memory (and not yet persited to the database) I get save errors.
When I look at the CollectionsToSave and CollectionsToDelete of the UnitOfWork, I see that they are all correct.
As soon as I have some time left I will try to replicate this. Kind regards, Wim
