Grid requests all virtual pages between two selected rows

[Yuliya]

Hi guys,

I get the following issue on the version 2014.2.0617.45:

When I select one row on top of the grid, then scroll down, and try to select other row - all the pages in between are getting loaded. The issue haven't reproduced on earlier version (2013.2.724.40).

Here is the code to reproduce the problem:
View:

<Window x:Class="RadGridView_Virtualization.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
        xmlns:local="clr-namespace:RadGridView_Virtualization"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <local:MyViewModel x:Key="MyViewModel" />
    </Window.Resources>

    <Grid DataContext="{StaticResource MyViewModel}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <telerik:RadGridView x:Name="gridAccessList"
                              Height="240"
                              Width="370"
                             IsFilteringAllowed="False" CanUserReorderColumns="True"
                              AutoGenerateColumns="False"
                              ItemsSource="{Binding Path=Items}"
                             EnableRowVirtualization="True"
                             SelectionMode="Extended"
                             ScrollViewer.IsDeferredScrollingEnabled="True" IsReadOnly="True"
                             ShowGroupPanel="False">
            <telerik:RadGridView.Columns>
                <telerik:GridViewDataColumn DataMemberBinding="{Binding Id}"
                                                            Width="*"/>
            </telerik:RadGridView.Columns>
        </telerik:RadGridView>
    </Grid>
</Window>

ViewModel:

using System.Collections.Generic;
using System.ComponentModel;
using Telerik.Windows.Data;

namespace RadGridView_Virtualization
{
    public class MyViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public MyViewModel()
        {
            Items = new VirtualQueryableCollectionView<DummyData>
              {
                VirtualItemCount = LoadSize, LoadSize = this.LoadSize
              };

          Items.ItemsLoading += OnItemsLoading;
        }

    private void OnItemsLoading(object sender, VirtualQueryableCollectionViewItemsLoadingEventArgs args)
    {
      Items.VirtualItemCount = 35000;

      Source = new List<DummyData>();

      for (int i = 0; i < args.ItemCount; i++)
      {
        Source.Add(new DummyData { Id = args.StartIndex + i });
      }

      Items.Load(args.StartIndex, Source);
    }

      private List<DummyData> source;
        public List<DummyData> Source
        {
            get { return this.source; }
            set { this.source = value; }
        }

        private int loadSize = 100;
        public int LoadSize
        {
            get { return loadSize; }
            set { loadSize = value; }
        }

        public VirtualQueryableCollectionView<DummyData> Items { get; private set; }

        public class DummyData
        {
            public int Id { get; set; }
        }
    }
}

If you put a breakpoint in OnItemsLoading method - you'll see that grid requests all pages between two selected rows. Please, note, that it happens after regular single row selection, so no data pages in the middle of two selected rows are not needed.

[Nick]

Hi Yulia,

Thank you for the provided information. We were able to reproduce the problem. I will post in this thread as soon as I have any further information on the matter. 


Regards,
Nik
Telerik

 

 

[Mads]

Hi Nik

Is there any updates on this issue?

[Nick]

Hi Mads,

We have still not found the exact cause of the problem. It is Reproducable only when the selection mode of RadGridView is Extended. We are working on pin pointing the exact problem, and will post as soon as there is any progress on the matter. 

Regards,
Nik
Telerik

 

 

[Yuliya]

Hi, Nick,

Is there any progress with the specified problem?
I've also noticed similar issue with Shift-selection between multiple pages: the data is loaded  twice! So, when I select some row, then scroll down to the grid, and close selection with Shift - all the pages between selected rows are retrieved twice.

I've checked both this issues on version 2013.2.724.40 - none of them existed.

[Nick]

Hi Yulia,

The issue is still not resolved. You can track the progress in our feedback portal.

Regards,
Nick
Telerik