Hello. I write WPF MVVM Prism 6 multimodule application. In some View (let us call it PeppyView) I have RadTreeView which bound to ObservableCollection located in PeppyViewModel. This radTreeView is populated with data from this ObservableCollection. In turn, the ObservableCollection is populated with data from binary *.DAT file when user is clicking on the 'Deserialize' RadButton. After populating with the data my RadTreeView is shown as collapsed RadTreeView. But I need that my RadTreeView is shown as expanded after its populating with data. Because ViewModel has to have no knowlage about the View in MVVM I can't call RadTreeView.ExpandAll method from ViewModel code. So how can I expand RadTreeView in my case? Is there a way to map UI control's method to ViewModule and call it there?