Question

OK, this must be a duplicate question, but I cannot find the answer:
I have a listbox that is databound to a Collection. By default Items[0] is selected. How can I prevent this in order to ensure that the SelectionChanged event is raised any time I click a ListBoxItem?

EDIT:
I had already dismissed the SelectedIndex=-1 route, but I tried again: Setting the SelectedIndex to -1 in the Listbox’s constructor (or as an attribute in XAML) does not work. It seems that the listbox is populated after the initialization and the selectedindex will become 0 after all.Same story for setting the SelectedItem to null;

I tried this:

<ListBox ItemsSource="{Binding Value}" 
         SelectionChanged="ListBox_SelectionChanged"
         IsSynchronizedWithCurrentItem="True"
         Loaded="ListBox_Loaded">
</ListBox>

with:

 private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if(e.AddedItems.Count==0)return;//Prevents stackoverflow! ;-)
        ((ListBox)e.OriginalSource).SelectedItem=null;
    }

private void ListBox_Loaded(object sender, RoutedEventArgs e)
{
    ((ListBox) sender).SelectedItem = null;
}

This works, BUT it inserts a blank line on top of the items that the listbox displays, which is very ugly….
In my particular case I could solve the problem by removing the IsSynchronizedWithCurrentItem attribute.

But I can think of many scenarios in which this would not be acceptable.

The above statement is nonsense: either you want to make use of master-detail binding and set the IsSynchronizedWithCurrentItem to true, or you don’t. It is rather unlikely that you want to make use of master-detail binding and then have no currently selected item in your listbox all the time

Answer 1

Use CollectionView as an ItemsSource for your list box. A fresh WPF project with no item initially selected:

XAML:

<Window x:Class="ListBoxDataBinding.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Grid>
    <ListBox 
        ItemsSource="{Binding Path=Value, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}}" 
        SelectionChanged="ListBox_SelectionChanged"
        IsSynchronizedWithCurrentItem="True"
        >
    </ListBox>
</Grid>
</Window>

cs:

public partial class Window1: Window {
    public IEnumerable Value {
        get { return (IEnumerable)GetValue(ValueProperty); }
        set { SetValue(ValueProperty, value); }
    }

    public static readonly DependencyProperty ValueProperty =
        DependencyProperty.Register("Value", typeof(IEnumerable), typeof(Window1), new UIPropertyMetadata(null));


    public Window1() {
        InitializeComponent();
        var view = new TheCollectionView();
        view.MoveCurrentTo(null);
        this.Value = view;
    }

    private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e) {
        MessageBox.Show("Selection changed");
    }
}

public class TheCollectionView: CollectionView {
    public TheCollectionView(): base(new TheCollection()) {
    }
}

public class TheCollection: List<string> {
    public TheCollection() {
        Add("string1");
        Add("string2");
        Add("string3");
    }
}