It seems in extended selection mode IsSelected
binding is buggy. Looks like only last item from selection which become out of scope is handled properly.
Demonstration:
Items 0
, 1
, 2
and 98
, 97
, 96
are selected with Control. When selecting 94
(without Control!) selection counter should be 1
, but you see 3
instead. Scrolling up reveals what only one (last) item of selection out of scope was unselected.
Below is mcve:
xaml:
<ListBox ItemsSource="{Binding Items}" SelectionMode="Extended" SelectionChanged="ListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Text}" />
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Setter Property="IsSelected" Value="{Binding IsSelected}" />
</Style>
</ListBox.ItemContainerStyle>
</ListBox>
cs:
public class NotifyPropertyChanged : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName] string property = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}
public class Item : NotifyPropertyChanged
{
bool _isSelected;
public bool IsSelected
{
get { return _isSelected; }
set { _isSelected = value; }
}
public string Text { get; set; }
}
public class ViewModel : NotifyPropertyChanged
{
public ObservableCollection<Item> Items { get; }
public ViewModel()
{
var list = new List<Item>();
for (int i = 0; i < 100; i++)
list.Add(new Item() { Text = i.ToString() });
Items = new ObservableCollection<Item>(list);
}
}
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new ViewModel();
}
void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
Title = ((ViewModel)DataContext).Items.Count(item => item.IsSelected).ToString();
}
}
A quick fix is to disable list control (ListBox
or ListView
) virtualization:
VirtualizingStackPanel.IsVirtualizing="False"
Question: any idea how to fix it without disabling virtualization?
See Question&Answers more detail:
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