[TabView] How to set the SelectedItem which not exits in Items?

[SongOfYouth]

Before 1.6, I can set the SelectedItem to a TabViewItem instance but not add it to the Items collection so it will not appear in the header and without any selected tab but displayed in the content, that's what i have just wanted! but it dosn't work same now(1.6.2), the page within the TabViewItem not added to the Items alway dispaly on the top of other tabs.