MaterialDesignToolToggleListBox with RadioButton behaviour

Background

I'm using the MaterialDesignToolToggleListBox for selecting one of up to three possible modes that can be available to the user. The current implementation of MaterialDesignToolToggleListBox will allow the user to unselect items in the list box which leaves us with no item selected.

Current Behaviour

Since i'm binding the SelectedValue of the ListBox I will get a binding/validation error since the SelectedItem will be null when the user unselect the item.

Expected Behaviour

Solutions

I would like to set a property on ListBoxAssist or use a new style to get a RadioButton behaviour on MaterialDesignToolToggleListBox.

1. Create a new style MaterialDesignToolRadioButtonListBox which uses RadioButton to achieve the desired result. (I have not tried this)
2. Use an attached property to hook into the SelectionChanged event and prevent unselect. Possible name could be PreventUnselect

Pseudo code for option 2

private void SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if(sender is ListBox listBox)
    {
        if (ListBoxAssist.GetIsToggle(listBox) &&
            listBox.SelectionMode == SelectionMode.Single)
        {
            if (e.AddedItems.Count == 0 && e.RemovedItems.Count == 1)
            {
                listBox.SelectedItem = e.RemovedItems[0];
            }
        }
    }            
}

Inizia individuando MaterialDesignToolToggleListBox e ListBoxAssist, quindi esamina come la selezione toggle gestisce SelectionChanged per i controlli ListBox a selezione singola. Confronta gli approcci proposti basati su style e attached property; il lavoro è completato quando l'elemento selezionato non può essere deselezionato e il binding di SelectedValue rimane valido.