Prism 6 with Unity - resolving view models for views without naming convention

Question

I am trying to have view models resolved using DI with Prism 6 and Unity in my WPF app and this works. However I don't know how to tell the framework which view should be merged with which view model.

If I use the convention, i.e. have ViewModels, and Views namespaces, and classes ViewA and ViewAViewModel everything works, however I would like to have more flexibility to name and organize my classes and this is why I want to somehow tell the framework explicitly which view goes with which view model. I tried many things, but nothing really works. Current "solution" makes app run but view model is not set.

Here is the code:

ViewA.xaml

<UserControl x:Class="WPFDITest.Views.ViewA"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:prism="http://prismlibrary.com/"
             prism:ViewModelLocator.AutoWireViewModel="True"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <StackPanel>
        <TextBlock Text="{Binding ViewAMessage}"/>
        <TextBox Text="{Binding ViewAMessage, UpdateSourceTrigger=PropertyChanged}"/>
    </StackPanel>
</UserControl>

MainWindow.xaml

<UserControl x:Class="WPFDITest.Views.ViewA"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:prism="http://prismlibrary.com/"
             prism:ViewModelLocator.AutoWireViewModel="True"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <StackPanel>
        <TextBlock Text="{Binding ViewAMessage}"/>
        <TextBox Text="{Binding ViewAMessage, UpdateSourceTrigger=PropertyChanged}"/>
    </StackPanel>
</UserControl>

ViewAVM.cs

public class ViewAVM : BindableBase
{
    private string viewAMessage;

    public ViewAVM(IModelA model)
    {
        viewAMessage = model.HelloMsgA();
    }

    public string ViewAMessage
    {
        get { return viewAMessage; }
        set { SetProperty(ref viewAMessage, value); }
    }
}

Model.cs

public interface IModelA
{
    string HelloMsgA();
}

public class ModelA : IModelA
{
    public string HelloMsgA()
    {
        return "Hello from A!";
    }
}

App.xaml.cs

public partial class App
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        var bootstraper = new Bootstrapper();
        bootstraper.Run();
    }
}

Bootstrapper.cs

public class Bootstrapper : UnityBootstrapper
{
    protected override DependencyObject CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void InitializeShell()
    {
        Application.Current.MainWindow.Show();
    }

    protected override void ConfigureContainer()
    {
        base.ConfigureContainer();
        Container.RegisterType<IModelA, ModelA>(new ContainerControlledLifetimeManager());
        Container.RegisterType<object, ViewAVM>("ViewA");
    }

    protected override void ConfigureViewModelLocator()
    {
        ViewModelLocationProvider.SetDefaultViewModelFactory(type => Container.Resolve(type));
    }
}

Answer 1

After some digging through Prism sources I found out how to do what I want. I can register each view with ViewModelLocationProvider.Register passing in a factory method for the view model. I created method that does just that with convenient syntax and uses container to resolve view model for given type:

public void BindViewModelToView<TViewModel, TView>()
{
    ViewModelLocationProvider.Register(typeof(TView).ToString(), () => Container.Resolve<TViewModel>());
}

And there is how I use it to bind ViewAVM to ViewA and ViewB both using same singleton instance.

public class Bootstrapper : UnityBootstrapper
{
    protected override DependencyObject CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void InitializeShell()
    {
        Application.Current.MainWindow.Show();
    }

    protected override void ConfigureContainer()
    {
        base.ConfigureContainer();
        Container.RegisterType<IModelA, ModelA>(new ContainerControlledLifetimeManager());
        Container.RegisterType<ViewAVM>(new ContainerControlledLifetimeManager());
    }

    protected override void ConfigureViewModelLocator()
    {
        BindViewModelToView<ViewAVM, ViewA>();
        BindViewModelToView<ViewAVM, ViewB>();
    }
}

By the way, as far as I can tell by the sources, it is only possible to associate view to view model through with ViewModelLocator by registering factories or by using their or custom convention, don't look for some DI magic.

Answer 2

Here is a link to Brian's blog on the ViewModelLocator, and it includes a section (Change those Nasty Conventions) on how to override the conventions if you would like.

Getting Started with Prism’s new ViewModelLocator

Personally, I set my DataContext in the code behind of the UserControl, in the constructor, after the View gets registered with the container in the Module. Conventions be damned!! :)

public ProductView(ProductViewModel view_model)
{
    InitializeComponent();
    DataContext = view_model;
}