Hi guys,

Using V2.0.0.0 und the self servicing scenario with C#:

If I want to load a single Entity on demand, I just access it like:

string x = myParentEnt.x;

If I want to load an entity collection, i have to write something like that:

OrderCollection orders = customer.Orders; Or: OrderCollection orders = customer.GetMultiOrders(false);

All of that I understand and it works fine, but what about that: OrderEntity ent = (OrderEntity)customer.Orders[0];

I this case, the Orders collection is not loaded and i get an "wrong index" error (of course). I would have to write:

OrderCollection orders = customer.Orders; OrderEntity ent = (OrderEntity)orders[0];

Am I right? Do I really have to write these two lines just to get one entity? Or did I miss something? I think the one line approach is much easier to write, isn't it?

Thanks for your answers!

I can't reproduce it.

[Test]
public void WrongLazyLoadingTriggerTest()
{
    CustomerEntity customer = new CustomerEntity("CHOPS");
    OrderEntity order = customer.Orders[0]; // should trigger lazy loading first. 
}

works fine. I also see 2 queries being executed: one for customer and one for its orders... As lazy loading is implemented in the generated code, could you set a breakpoint into the property for the child collection and see what code is executed?

Otis, thanks for your answer.

If I access the Property, GetMulti_EntityName_(false) is executed. But the _alreadyFetched-Property is always TRUE when the method "GetMulti[i]EntityName[/i](bool forceFetch, IEntityFactory entityFactoryToUse, IPredicateExpression filter)" later on.

Since I now know it should be possible, here's the complete Code. Perhaps something else is wrong. (bsKapital, bsPerson1 and bsPerson2 are BindingSources)

VorgabeKapital.FetchUsingPK(3);
bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

Using this, I get the correct results:

            
IPrefetchPath prefetchPath = new PrefetchPath((int)Data.EntityType.VorgabePersonEntity);
prefetchPath.Add(VorgabeKapitalEntity.PrefetchPathVorgabePerson);

VorgabeKapital.FetchUsingPK(3, prefetchPath);
bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

This works, too:

VorgabeKapital.FetchUsingPK(3); 
VorgabeKapital.GetMultiVorgabePerson(true);

bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

But that's not lazy loading, is it? Do I have to do something to enable lazy loading? I didn't find anything in the documentation, but perhaps I simply missed it.

Sokon1 wrote:

Otis, thanks for your answer.

If I access the Property, GetMulti_EntityName_(false) is executed. But the _alreadyFetched-Property is always TRUE when the method "GetMulti[i]EntityName[/i](bool forceFetch, IEntityFactory entityFactoryToUse, IPredicateExpression filter)" later on.

Then the fetch already took place. Be aware that it is tricky to debug: if you have open a watch in the debugger which reads the collection property, it will trigger lazy loading and load the collection.

Since I now know it should be possible, here's the complete Code. Perhaps something else is wrong. (bsKapital, bsPerson1 and bsPerson2 are BindingSources)

VorgabeKapital.FetchUsingPK(3);
bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

It's a little tricky. You set VorgabeKapital as the datasource for bsKapital, which could have a DataMember set to VorgabePerson and a grid could be bound to that too. IF that's the case, at this line: bsKapital.DataSource = this.VorgabeKapital; the VorgabePerson collection is fetched first.

at this line: bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0]; VorgabePerson is fetched for the first time, if bsKapital isn't bound to a grid and datamember isn't set to VorgabePerson.

and when you access the property again on this line: bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1]; The collection is already fetched so the same collection is returned. If there was just 1 entity, this gives an exception.

Using this, I get the correct results:

            
IPrefetchPath prefetchPath = new PrefetchPath((int)Data.EntityType.VorgabePersonEntity);
prefetchPath.Add(VorgabeKapitalEntity.PrefetchPathVorgabePerson);

VorgabeKapital.FetchUsingPK(3, prefetchPath);
bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

As you fetch the data up front, lazy loading isn't triggered here at all, as the data is already fetched

This works, too:

VorgabeKapital.FetchUsingPK(3); 
VorgabeKapital.GetMultiVorgabePerson(true);

bsKapital.DataSource = this.VorgabeKapital;
bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

At this line you fetch the data: VorgabeKapital.GetMultiVorgabePerson(true);

so any code accessing the property won't trigger lazy loading, as the data is already fetched.

But that's not lazy loading, is it? Do I have to do something to enable lazy loading? I didn't find anything in the documentation, but perhaps I simply missed it.

Lazy loading is automatic, however it of course doesn't fetch the data over and over again: if it's fetched once, it won't fetch it again. You can force it to refetch the data by passing true to the getmulti method.

Hell yes! The Debugger! That was the right hint. Thanks!

So for those with the same problem: here is what I found out:

* VorgabeKapital.FetchUsingPK(3); 
  bsKapital.DataSource = this.VorgabeKapital;
  bsPerson1.DataSource = this.VorgabeKapital.VorgabePerson[0];
  bsPerson2.DataSource = this.VorgabeKapital.VorgabePerson[1];

If there is a breakpoint at the line marked by the '*' and there is a watch on 'this.VorgabeKapital.VorgabePerson[0];' The lazy loading tries to fetch the collection of a entity, which is not fetched yet. So the watch shows an exception. The problem is: By trying to fetch the collection the _alreadyFetched-Property is set to true (couldn't this be changed by you LLBLGen-developers?). If you access the VorgabePerson collection later, the collection won't be fetched again and - BANG

If you remove the breakpoint, everything is fine.

Thanks again for your help, Otis!