[Solved] In 2010 Q3 RadGridView fails when using DeferRefresh

[Alex]

Hello!
I have a PagedCollectionView in my view model and RadGridView in XAML with ItemsSource binded to PagedCollectionView.
When i try to call View.SortDescriptions.Clear() inside the scope of DeferRefresh()
RadGridView fails with InvalidOperationException:
Cannot change or check the contents or current position of the PagedCollectionView while Refresh is being deferred.

Here is my xaml:

<UserControl x:Class="RadGridViewTest.MainPage"
             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:RadGridViewTest">
    <UserControl.Resources>
        <local:MainPageViewModel x:Key="viewModel" />
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" DataContext="{StaticResource viewModel}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <telerik:RadGridView ItemsSource="{Binding View}" />
        <Button Grid.Row="1" Margin="5" Content="Clear sorting"
                Command="{Binding ClearSorting}" HorizontalAlignment="Center" />
    </Grid>
</UserControl>

and view model:

using System;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Data;
using System.Windows.Input;
namespace RadGridViewTest
{
    public class MainPageViewModel
    {
        private readonly ObservableCollection<string> _innerCollection;
        public MainPageViewModel()
        {
            _innerCollection = new ObservableCollection<string> { "Taganrog", "Cherven Bryag" };
            View = new PagedCollectionView(_innerCollection);
            ClearSorting = new DelegateCommand(onExecuteClearSorting);
        }
        public ICommand ClearSorting { get; private set; }
        public PagedCollectionView View { get; private set; }
        private void onExecuteClearSorting()
        {
            using (View.DeferRefresh()) // Comment this line to avoid exception
            {
                try { View.SortDescriptions.Clear(); } // This is the problem!!!
                catch (Exception ex) { MessageBox.Show(ex.Message); }
            }
        }
    }
    public class DelegateCommand : ICommand
    {
        private readonly Action _executeAction;
        public DelegateCommand(Action executeAction)
        {
            _executeAction = executeAction;
        }
        public bool CanExecute(object parameter) { return true; }
        public void Execute(object parameter) { _executeAction(); }
        public event EventHandler CanExecuteChanged;
    }
}

When i commented line with using (View.DeferRefresh()) no exception occured.
Standart DataGrid also works well with DeferRefresh.

[Yavor Georgiev]

Hi Alex,

 Unfortunately there is little we can do about this error, as ICollectionView does not expose a flag, signalling if it's deferring a refresh. What you can do is use our QueryableCollectionView in your ViewModel and bind RadGridView to that.

Best wishes,
Yavor Georgiev
the Telerik team

[Alex]

Thanks. It works.