How to bind SelectedItems.Count and Items.Count of ListBox in ViewModel's property?

Question

In xaml this works:

<TextBlock HorizontalAlignment="Right">
    <Run Text="{Binding ElementName=lb, Path=SelectedItems.Count, Mode=OneWay}"/>
    <Run Text="/"/>
    <Run Text="{Binding ElementName=lb, Path=Items.Count, Mode=OneWay}"/>
    <Run Text=" excluded"/>
</TextBlock>

Can I bind these to properties in ViewModel?

Answer 1

Not that hard but it took a while to figure out! I've to extend a ListBox with two DependencyProperty, Total and Selected. In OnSelectionChanged I've to set the Selected = SelectedItems.Count and in OnItemsChanged I've to set Total = Items.Count. Those Total and Selected can be bound to ViewModel's property.