PoC.CaliburnSharedViews

I've run across an issue using Caliburn.Micro when sharing a Screen between multiple parent Screens. In this example I have 2 tabs inside a shell. Each tab shares a single instance of SharedViewModel (essentially a singleton).

var shared = new SharedViewModel();

Items.AddRange(new []
{
    new TabViewModel { Shared = shared },
    new TabViewModel { Shared = shared },
});

And each tab's view has a ContentControl bound to the Shared property which is SharedViewModel:

<ContentControl cal:View.Model="{Binding Shared}"/>

Here's the order of events:

1. Start the app. See the shared view.
2. Switch to second tab. See the shared view.
3. Switch back to first tab. Shared view is gone.
4. Switch to second tab again. The shared view is there.
5. Proceed to pull hair out.