如何将WPF控件的内容绑定到其容器的DataContext，以便我可以基于该对象应用DataTemplateSelector？

I'm trying to bind a WPF window atop a ViewModel that contains two collections, A and B. I'm attempting to use DataTemplates to display either A or B depending on the setting of a flag in my ViewModel.I'm trying to bind a WPF window atop a ViewMode