Question

I want to bind my TextBlock.Text to ListBox.SelectedItems.Count, but I find that when I multi-select items in my listBox, my TextBlock doesn’t show anything.

I remember this way works in WPF, but it doesn’t work in Windows Store App anymore.

Is there any alternative way to solve the simple problem ?

   <StackPanel>
        <StackPanel.Resources>
            <local:NumberToTextConverter x:Key="NumToText" />
        </StackPanel.Resources>
        <TextBlock Text="{Binding SelectedItems.Count, ElementName=listBox, Mode=TwoWay, Converter={StaticResource NumToText}}"
                   Height="80" />
        <ListBox x:Name="listBox"
                 SelectionMode="Multiple" />
    </StackPanel>

Here is the converter, but it’s not necessary in this case.

internal class NumberToTextConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string culture)
    {
        if(value != null)
            return ((int)value).ToString();

        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, string culture)
    {
        throw new NotImplementedException();
    }

}

I load some data at the entry main of the program.

        List<string> gogoString = new List<string>();

        for (int i = 0; i < 4; i++)
            gogoString.Add(i.ToString());

        listBox.ItemsSource = gogoString;

Answer 1

Ok, I am late to find the answer.

The ListBox implements INotifyPropertyChanged in WPF but not in Windows Store app. That’s why I can’t get notified from ListBox.Items.Count or ListBox.SelectedItems.Count in Windows Store app.