设置默认键盘焦点加载UserControl

I have an MVVM setup with a mainwindow that contains a ContentControl. I set this to a particular viewmodel which then maps to a view. A view is a usercontrol. I want to be able to set the default keyboard focus to a default element in the usercontrol(View) when it loads so the application can eventually be driven just by using up, down, left, right and enter. Some of my failed attempts are settingI have an MVVM setup with a mainwindow that con