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

Not satisfied with the given answers I was trying to find one by myself... Well it turns out to be more like a hack then a solution but for me that works fine. This Solution uses MultiBindings in a special way. First it may look like a ton of Code but you can reuse it with very little effort.

First I implemented a 'IMultiValueConverter'

public class SelectedItemsMerger : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        SelectedItemsContainer sic = values[1] as SelectedItemsContainer;

        if (sic != null)
            sic.SelectedItems = values[0];

        return values[0];
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        return new[] { value };
    }
}

And a SelectedItems Container/Wrapper:

public class SelectedItemsContainer
{
    /// Nothing special here...
    public object SelectedItems { get; set; }
}

Now we create the Binding for our ListBox.SelectedItem (Singular). Note: You have to create a static Resource for the 'Converter'. This may be done once per application and be reused for all ListBoxes that need the converter.

In the ViewModel I created the Container where I can bind to. It is important to initialize it with new() in order to fill it with the values.

    SelectedItemsContainer selectionContainer = new SelectedItemsContainer();
    public SelectedItemsContainer SelectionContainer
    {
        get { return this.selectionContainer; }
        set
        {
            if (this.selectionContainer != value)
            {
                this.selectionContainer = value;
                this.OnPropertyChanged("SelectionContainer");
            }
        }
    }

And that's it. Maybe someone sees some improvements? What do You think about it?