ViewModels references in ShellViewModel Caliburn.Micro - mvvm

Question

In this thread : Can anybody provide any simple working example of the Conductor<T>.Collection.AllActive usage? I've had part of an answer but I'm still a but confused.
I would simply like to reference all my view models into my ShellViewModel to be able to open/close ContentControls, but without injecting all of them in the constructor.
In the answer, it is suggested to inject an interface in the constructor of the ShellViewModel. If I do that, do I have to inject all my ViewModels in a class that implements that interface?
public MyViewModel(IMagicViewModelFactory factory)
{
FirstSubViewModel = factory.MagicallyGiveMeTheViewModelIWant();
SecondSubViewModel = factory.MagicallyGiveMeTheViewModelIWant();
ThirdSubViewModel = factory.MagicallyGiveMeTheViewModelIWant();
Items.Add(FirstSubViewModel);
Items.Add(SecondSubViewModel);
Items.Add(ThirdSubViewModel);
}
Also, I would like to avoid going through IoC.Get<> to get the instances of my view Models, I think it violates the principles of IoC if I am not mistaken.
In a few other examples, they create new viewModels when needed, but what's the point of using IoC in that case, especially when I need services injected inside those new ViewModels?
In my Shell view, I have a layout with 3 different areas, bound to my shell view model by :
<ContentControl x:Name="Header"
Grid.ColumnSpan="3"/>
<ContentControl x:Name="Menu"
Grid.Row="1"/>
<ContentControl x:Name="Main"
Grid.ColumnSpan="3"/>
In my ShellViewModel extending Conductor.Collection.AllActive, I reference the 3 areas like this:
public Screen Menu { get; private set; }
public Screen Header { get; private set; }
public Screen Main { get; private set; }
I would like to be able to change them like so:
Menu = Items.FirstOrDefault(x => x.DisplayName == "Menu");
Header = Items.FirstOrDefault(x => x.DisplayName == "Header");
Main = Items.FirstOrDefault(x => x.DisplayName == "Landing");
All my ViewModels have a DisplayName set in their constructor.
I have tried this but GetChildren() is empty
foreach (var screen in GetChildren())
{
Items.Add(screen);
}
Am I missing something obvious?
Thanks in Advance!

Answer 1

Finally, I managed to find an answer myself. It's all in the AppBootstrapper!
I ended up creating a ViewModelBase for my Screens so that they could all have an IShell property (so that the ViewModels could trigger a navigation in the ShellViewModel) like so:
public class ViewModelBase : Screen
{
private IShell _shell;
public IShell Shell
{
get { return _shell; }
set
{
_shell = value;
NotifyOfPropertyChange(() => Shell);
}
}
}
then in the AppBoostrapper registered them like this :
container.Singleton<ViewModelBase, SomeViewModel>();
container.Singleton<ViewModelBase, AnotherViewModel>();
container.Singleton<ViewModelBase, YetAnotherViewModel>();
then created an IEnumerable to pass as param to my ShellViewModel ctor:
IEnumerable<ViewModelBase> listScreens = GetAllScreenInstances();
container.Instance<IShell>(new ShellViewModel(listScreens));
then passing the IShell to each ViewModels
foreach (ViewModelBase screen in listScreens)
{
screen.Shell = GetShellViewModelInstance();
}
for the sake of completeness, here are my GetAllScreenInstances() and GetShellViewModelInstance() :
protected IEnumerable<ViewModelBase> GetAllScreenInstances()
{
return container.GetAllInstances<ViewModelBase>();
}
protected IShell GetShellViewModelInstance()
{
var instance = container.GetInstance<IShell>();
if (instance != null)
return instance;
throw new InvalidOperationException("Could not locate any instances.");
}
Here's what my ShellViewModel ctor looks like:
public ShellViewModel(IEnumerable<ViewModelBase> screens )
{
Items.AddRange(screens);
}
Hope this can help someone in the future!