Caliburn.Micro + Unity 2.1 + MVVM: example code - mvvm

Question

I'm trying to implement Unity in a WPF MVVM application, but I'm missing the big picture.
At this moment I have created a bootstrapper like this:
public class MainBootstrapper : Bootstrapper<MainViewModel>
{
private UnityContainer container;
protected override void Configure()
{
container = new UnityContainer();
container.RegisterType<IServiceLocator, UnityServiceLocator>(new ContainerControlledLifetimeManager());
container.RegisterType<IWindowManager, WindowManager>(new ContainerControlledLifetimeManager());
container.RegisterType<IEventAggregator, EventAggregator>(new ContainerControlledLifetimeManager());
}
protected override object GetInstance(Type service, string key)
{
if (service != null)
{
return container.Resolve(service);
}
if (!string.IsNullOrWhiteSpace(key))
{
return container.Resolve(Type.GetType(key));
}
return null;
}
protected override IEnumerable<object> GetAllInstances(Type service)
{
return container.ResolveAll(service);
}
protected override void BuildUp(object instance)
{
container.BuildUp(instance);
}
}
How what is the best way to use this?
This code currently works:
public class MainViewModel : PropertyChangedBase
{
public MainViewModel()
{ }
[Dependency]
public Sub1ViewModel Sub1VM { get; set; }
[Dependency]
public Sub2ViewModel Sub2VM { get; set; }
}
the MainView has this:
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<ContentControl Grid.Row="0" Name="Sub1VM" />
<ContentControl Grid.Row="1" Name="Sub2VM" />
</Grid>
First of all: the code that I shared, is this the correct way of using Unity + Caliburn?
Now let's say that my Sub1VM uses a model 'M1', but Sub2VM needs to use the same model to display information but not by making another instance of model M1. (singleton)
How does this work now? Show I use a IServiceLocator in each viewmodel constructor? Could somebody share a code sample to explain it?

Answer 1

First of all i agree with McDonnellDean that you should read the article about the Screens, Conductors and Composition (if i were you i would read all the articles before that too to understand how Caliburn.Micro works.). Besides that, you implemented Unity correctly and you can check Unity as IoC Container for Caliburn.Micro for more information. On the other side you are mixing two concepts here, namely Dependency Injection and MVVM. Regarding your question about the model, i would also prefer constructor injection, and if you want a single instance of the model, perhaps you can inject a Factory that creates that model for you and wrap it into two different view models and expose it through the two different properties. At last i really encourage you to read the tutorials (start here), at least the basic topics.

Answer 2

I don't know Unity in particular but your configuration looks correct.
As for your injection points. I would say that rather than doing property injection you should do constructor injection. What you are doing is fine, however you may want to look up screens and conductors, these allow you to add life-cycle to your ViewModels. Typically it would look like this:
Bootstrapper opens ShellViewModel
ShellViewModel takes in MainViewModel via Ctor injection as an IConductorOneActive
MainViewModel takes a collection of IScreens.
ShellViewModel calls MainViewModels activate method on MainViewModel.
See Screens, Conductors and Composition. As I stated above, your way is fine but it is a little on the manual side and means you have to wire everything by hand.