Caliburn Mico: Screen's ActivateItem.DisplayName Property does not bind to Window Title automatically

Question

I am trying to figure out why Caliburn.Micro isnt binding my Screen DisplayName Property to the Window Title out of the box.

I read this post: https://stackoverflow.com/a/9072035/2111892 So, shouldn't it be bound without doing it manually?

My conductor looks like this:

[Export(typeof (ShellViewModel))]
public class ShellViewModel : Conductor<Screen>, IHandle<IViewModelMessage>
{
    [ImportMany(typeof (IViewModelMessageHandler))]
    private IEnumerable<IViewModelMessageHandler> _messageHandlers;

    [ImportingConstructor]
    public ShellViewModel(IEventAggregator eventAggregator)
    {
        eventAggregator.Subscribe(this);
    }

    protected override void OnActivate()
    {
        var viewModel = IoC.Get<LoginViewModel>();
        ActivateItem(viewModel);
    }
}

... while my Screen is looking like this:

[Export(typeof(LoginViewModel))]
public class LoginViewModel : Screen
{
    [ImportingConstructor]
    public LoginViewModel(IEventAggregator eventAggregator, IMessageService messageService, IClient client, IClientReceiver receiver, IClientTransceiver transceiver)
    {
        DisplayName = "Login";
    }
}

Have I made a mistake or did I understand something incorrectly?

Edit:\

ShellView btw looks like this:

<UserControl x:Class="Test.Client.Gui.Views.ShellView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="900"
    Width="1000">
<Grid VerticalAlignment="Center">
    <ContentControl x:Name="ActiveItem" />
</Grid>
</UserControl>

Answer 1

The Title will bind to the DisplayName of your ShellViewModel, not to any viewmodels you create inside. You will have to change the DisplayName whenever you activate a child view model. Or explicitly bind it with Title="{Binding ActiveItem.DisplayName}".

Answer 2

I actually like the following solution when you have a conductor like that

<Window>
    <Window.Title >
        <PriorityBinding>
            <Binding Path="ActiveItem.DisplayName" Converter="{StaticResource NullToUnsetConverter}"></Binding>
            <Binding Path="DisplayName"></Binding>
        </PriorityBinding>
    </Window.Title>
</Window>

NullToUnsetConverter just allows the binding to fall through if the active item sets it's own displayname to null. If you don't need that behaviour you can just omit it entirely.