如何在ViewModels之间正确共享Entity Framework ContextObject？

I'm a newbie with WPF/MVVM/Entity Framework and it's a lot of concepts to handle simultaneously. I'm creating a WPF app with only one main View, which is splitted in 2 parts : 1 UserControl for a Master view of my data, another userControl for the detailed view. All data is stored in database generated via Entity Framework entity model.I'm a newbie with WPF/MVVM/Entity Framework and