Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.AllowItemCommand}"
[http://stackoverflow.com/questions/1127933/wpf-databinding-how-do-i-access-the-parent-data-context]
Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.AllowItemCommand}"
[http://stackoverflow.com/questions/1127933/wpf-databinding-how-do-i-access-the-parent-data-context]