How to support ListBox SelectedItems binding with MVVM in a navigable application

Question

I am making a WPF application that is navigable via custom \"Next\" and \"Back\" buttons and commands (i.e. not using a NavigationWindow). On one screen, I have

Answer 1

I couldn't get Rachel's solution to work how I wanted it, but I found Sandesh's answer of creating a custom dependency property to work perfectly for me. I just had to write similar code for a ListBox:

public class ListBoxCustom : ListBox
{
    public ListBoxCustom()
    {
        SelectionChanged += ListBoxCustom_SelectionChanged;
    }

    void ListBoxCustom_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        SelectedItemsList = SelectedItems;
    }

    public IList SelectedItemsList
    {
        get { return (IList)GetValue(SelectedItemsListProperty); }
        set { SetValue(SelectedItemsListProperty, value); }
    }

    public static readonly DependencyProperty SelectedItemsListProperty =
       DependencyProperty.Register(nameof(SelectedItemsList), typeof(IList), typeof(ListBoxCustom), new PropertyMetadata(null));

}

In my View Model I just referenced that property to get my selected list.