DevForce 2010: filtering related collections

filtering related collections

Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce 2010
Forum Discription: For .NET 4.0
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=3221
Printed Date: 13-May-2026 at 11:36am

Topic: filtering related collections

Posted By: voulgeor
Subject: filtering related collections
Date Posted: 18-Jan-2012 at 9:11am

hi i have an entity called item

like this

itemID

itemCode

itemPrice

there is a related entity called ItemDescriptions

like this

itemID

Description

LanguageId

when i run the query

dim k=from t in manager.item where t.itemid=15 select t

i get correctly

the item which has id 15

but in the k.ItemDescriptions collection i get all the six description of the item 15 for the 6 different languages (correctly again).

is there a way to form the query in such a way to filter that collection so it has only one description that with languageid=20?

thanks

Replies:

Posted By: sbelini
Date Posted: 18-Jan-2012 at 3:56pm

Hi voulgeor,

In you case, you might want to retrieve the ItemDescription with languageid=20 manually and set the EntityReferenceLoadStrategy to DoNotLoad.

You can find more information about Navigation Properties and EntityReferenceStrategy in the http://drc.ideablade.com/xwiki/bin/view/Documentation/navigation-properties-data-retrieval - DevForce Resource Center .

Silvio.

Posted By: voulgeor
Date Posted: 19-Jan-2012 at 2:38am

i am sorry i didnt get that ..

the languageid depends on the customer that the order goes

it changes the description of the item according to customer checking the item.

i am new to devforce can you provide me with an example as i did?

thanks again and sorry

Posted By: sbelini
Date Posted: 19-Jan-2012 at 3:49am

Hi voulgeor,

No problem. You can set the DefaultEntityReferenceStrategy for the EntityManager:

manager.DefaultEntityReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)

or for the EntityType:

Item.PropertyMetadata.ItemDescriptions.ReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)

or even for the given entity only: (by setting GetEntityReference.IsLoaded to true)

Item.PropertyMetadata.ItemDescriptions.GetEntityReference(item).IsLoaded = True

Then can still use your same query to retrieve item and once you have it, you can query for the itemdescription given the languageid criteria.

This way you can navigate to Item.ItemDescriptions and will only retrieve the itemdescription matching the languageid given (since it's the only one in cash and we are not accessing the datasource)

Another way, maybe simpler, would be to filter the navigation property as you retrieve it:

Dim itemdescriptions = item.ItemDescriptions.Where(Function(id) id.LanguageId == languageid)

Regards,

Silvio.

Posted By: voulgeor
Date Posted: 20-Jan-2012 at 6:07am

it doesnt work for me...

i have used

	    SaleItem.PropertyMetadata.SaleItemslanguages.ReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)
 
            Dim kk = (From t In ctx.SaleItemslanguages Where t.LanguagesID = 20).ToList
 
            Dim k = (From t In ctx.SaleItems.Include("SaleItemslanguages") Where t.SaleItemsID = 15 Select t).ToList

the k.SaleItemslanguages

again contains 6 rows...

how should i fill the SaleItemslanguages collection so it will be used as described in the cache

what am i doing wrong?

i am new to this.

thanks for your help

Posted By: voulgeor
Date Posted: 23-Jan-2012 at 8:44am

an example of the procedure

so it works would be nice thanks

Posted By: sbelini
Date Posted: 23-Jan-2012 at 9:27am

Hi voulgeor,

You should not have the Include statement in your query as it will force a trip to the datasource:

Dim k = (From t In ctx.SaleItems~~.Include("SaleItemslanguages")~~ Where t.SaleItemsID = 15 Select t).ToList

Regards,

Silvio.

Posted By: voulgeor
Date Posted: 23-Jan-2012 at 11:13am

thanks for your help

now after doing that in my wpf form

the ui bind to the saleitems works fine

but the listbox that is bind to saleitems.SaleItemslanguages

shows nothing.

iam just seting the binding contex to the selected saleitem.

the navigation to SaleItemslanguages finds nothing to return

if i remark the

  SaleItem.PropertyMetadata.SaleItemslanguages.ReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)

it works as expected (because i guess goes back to the sql server)

but again shows all the values and not the filtered ones.

Posted By: sbelini
Date Posted: 23-Jan-2012 at 1:07pm

Hi voulgeor,

I'm confused.

The listbox binding to salesitems.SaleItemsLanguages should show only one element (the same as in k.SaleItemslanguages)

If you need all salesitems in cache to be able to populate your listbox, you will not be able to bind the your ui directly to the navigation property (i.e. k.SaleItemslanguages).

You are doing your binding in the XAML, right? Try instead doing the binding on code:

i.e.

mySalesItemsLanguagesGrid.ItemsSource = someSaleItem.ItemDescriptions.Where(Function(id) id.LanguageId == languageid)

Silvio.

Posted By: voulgeor
Date Posted: 23-Jan-2012 at 2:41pm

no each time

i display one saleitem only

the listbox displays the

saleitem.SaleItemslanguages

as you said

but the problem is that

it doesnt have any items to be displayed.

it doesnt display any elements if

i have

 SaleItem.PropertyMetadata.SaleItemslanguages.ReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)

and fill the SaleItemslanguages with the filtered query

the navigated k.SaleItemslanguages is empty (should have only one element).

it should display the one filtered description isnt?

BUT if i put in remark

the  SaleItem.PropertyMetadata.SaleItemslanguages.ReferenceStrategy = New EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.OverwriteChanges)

then it displays correctly (i suppose because it goes to the sql database to fetch the values)
but as expected all the 6 values for the selected saleitem show up (not filtered).

if the referencestrategy is set DoNotLoad it doesnt go to the database (correctly)
but also  doesnt  navigate to the cached entity that we load manualy previously (to return that one element)

Posted By: sbelini
Date Posted: 23-Jan-2012 at 4:30pm

Can you create a simple test solution (against NorthwindIB please) demonstrating your issue and upload it here?

Thanks,

Silvio.