MultiSelectionComboBox / MultiSelectorHelper.SelectedItems one step behind

[TheCamel]

Describe the bug

The collection filled by the MultiSelectorHelper is not sync ; but one step behind when using the associated event. seems that client receive the mscb_Example_SelectionChanged event before the helper.

<mah:MultiSelectionComboBox x:Name="mscb_Example"
....
mah:MultiSelectorHelper.SelectedItems="{Binding SelectedAnimals}"

Steps to reproduce

in the sample application, place a breakpoint here, and check the SelectedAnimals collection - it is allways one counter behind

private void mscb_Example_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (var item in e.AddedItems)

Expected behavior

the problem is that i whant to use the selection changed event to refresh filters...but the collection is not uptodate

Environment

MahApps.Metro version: v3.0.0 - 0476
Target Framework: .Net Core 8