RadGridView, Paging, QueryableCollectionView & EntityFramework

[Koen]

Hello All,

I'm trying to setup the following scenario, running version 2013.2.724.40:

• On my ViewModel, I have a QueryableCollectionView, with an EntityFramework IQueryable as it's source
• I have a DataGrid, bound to this QueryableCollectionView
• I have a DataPager, linked to this DataGrid

<telerik:RadGridView x:Name="radGridView"
         ItemsSource="{Binding MyQueryableCollectionView}"
         AutoGenerateColumns="True" />
<telerik:RadDataPager
         Source="{Binding Items, ElementName=radGridView}"
         PageSize="10" DisplayMode="All" />

When I run this app, everything looks fine:

• A query is ran on the db, selecting the top 10 records for the first page
• The DataGrid shows the first page, 10 records
• The DataPager calculates the correct number of pages

However, when I move to the second, third, .. page, the page is empty.
No new query is ran on the db to select the next 10 records.

Is this kind of scenario not supported out of the box?



Notes:

• It does work when I load the entire record set when creating the QueryableCollectionView
  (of course, I do NOT want to do this, that's why I use paging)
• I also tried by binding the DataPager Source to the QueryableCollectionView, but this has the same behavior.
  

  <telerik:RadGridView
           ItemsSource="{Binding MyQueryableCollectionView}"
           AutoGenerateColumns="True" />
  <telerik:RadDataPager
           Source="{Binding MyQueryableCollectionView}"
           PageSize="10" DisplayMode="All" />

[Koen]

For future reference, I've found a solution to this problem:

The IQueryable that you set as the source of the QueryableCollectionView MUST be ordered. 
Otherwise, you'll get the behavior described in this post.

I guess this makes sense in some way;
If you're not ordering the IQueryable, Entity Framework is unable to execute skip methods on it;
Underlying, this exceptions occurs: 

The method 'Skip' is only supported for sorted input in LINQ to Entities. The method 'OrderBy' must be called before the method 'Skip'.

Regards,
Koen

[Dimitrina]

Hi,

Thank you for sharing your solution with the community. 

Regards,
Didie
Telerik