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];
            }
        }
    }            
}

首先定位 MaterialDesignToolToggleListBox 和 ListBoxAssist，然后检查切换选择如何处理单选 ListBox 控件的 SelectionChanged。比较提议的 style 和 attached property 方案；完成的标准是无法清除所选项，同时 SelectedValue 绑定仍然有效。