VirtualizingStackPanel + MVVM + multiple selection

Question

I have implemented a selection pattern similar to the one described in this post using a ViewModel to store the IsSelected value, and by binding the ListViewItem.IsSel

Answer 1

In my case, I ended up solving this by deriving a ListBoxEx class from ListBox, and adding code to respond to selection changes, enforcing the selection state on the item view models:

private readonly List selectedItems = new List();

protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
    base.OnSelectionChanged(e);

    bool isVirtualizing = VirtualizingStackPanel.GetIsVirtualizing(this);
    bool isMultiSelect = (SelectionMode != SelectionMode.Single);

    if (isVirtualizing && isMultiSelect)
    {
        var newSelectedItems = SelectedItems.Cast();

        foreach (var deselectedItem in this.selectedItems.Except(newSelectedItems))
        {
            deselectedItem.IsSelected = false;
        }

        this.selectedItems.Clear();
        this.selectedItems.AddRange(newSelectedItems);

        foreach (var newlySelectedItem in this.selectedItems)
        {
            newlySelectedItem.IsSelected = true;
        }
    }
}