title: Commands from Details view of MVVM Master/Details app fail
body: <p>Learning MVVM\WPF\C# by building a simple master\details app. I have a MainView which holds the MasterView, DetailView, and ControlsView. I have added buttons (ICommand) to all views. They all work properly except the one on the DetailView. The problem is the view's datacontext (DataContext="{Binding SelectedMediaItem}"). On the DetailView, if I add a main grid to hold the SelectedMediaItem grid and then add a button the main grid it works fine. Any ideas how I can add a button next to a textbox in the SelectedMediaItem grid? Thank You  </p>