Prism 6.1 ViewModelLocator doesn't instantiate my ViewModel

Question

I just set up a new project recently, using Prism 6.1(with Unity).

I've my bootstrapper:

public class ServerBootstrapper : UnityBootstrapper
{
    protected override DependencyObject CreateShell()
    {
        return Container.Resolve<MainShell>();
    }
    protected override void InitializeShell()
    {
        base.InitializeShell();
        Application.Current.MainWindow = (Window)Shell;
        Application.Current.MainWindow.Show();
    }
    protected override void ConfigureModuleCatalog()
    {
        base.ConfigureModuleCatalog();
        ModuleCatalog catalog = (ModuleCatalog)ModuleCatalog;
        catalog.AddModule(typeof(ServerUIModule));
    }
}

The MainShell:

<Window.Resources>
    <Style TargetType="TabItem">
        <Setter Property="Header" Value="{Binding DataContext.Title}" />
    </Style>
</Window.Resources>
<DockPanel LastChildFill="True">
    <TabControl regions:RegionManager.RegionName="{x:Static infrastructure:RegionsNames.MAIN_TAB_REGION}" />
</DockPanel>

My Module definition:

public class ServerUIModule : IModule
{
    private readonly IRegionManager m_regionManager;

    public ServerUIModule( IRegionManager regionManager)
    {
        m_container = container;
        m_regionManager = regionManager;
    }

    public void Initialize()
    {
        m_regionManager.RegisterViewWithRegion(RegionsNames.MAIN_TAB_REGION, typeof(StatusView));
        m_regionManager.RegisterViewWithRegion(RegionsNames.MAIN_TAB_REGION, typeof(LogMessagesView));
    }
}

My StatusView:

<UserControl x:Class="Xms.Server.UI.Views.StatusView"
             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:local="clr-namespace:Xms.Server.UI.Views"
             xmlns:mvvm="http://prismlibrary.com/"
             xmlns:statusControl="clr-namespace:Xms.Server.UI.Views.StatusControl"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300" Background="Aquamarine" mvvm:ViewModelLocator.AutoWireViewModel="True">
    <Grid>
        <TextBlock>Content</TextBlock>
    </Grid>
</UserControl>

The corresponding ViewModel:

public class StatusViewModel : BindableBase
{
    public String Title => LocalizedResources.StatusModuleTitle;

    public StatusViewModel()
    {
        //This constructor is never called
    }
}

The issue is that my constructor is never called, my DataContext is not set.

How can I debug this? What could I've done wrong?

Answer 1

First, make sure that the views reside in a Views namespace, and the viewmodels in ViewModels, respectively.

Second, the easiest way of debugging this type of things is copying some code from the prism sources and put this in MyBootstrapper.ConfigureContainer:

ViewModelLocationProvider.SetDefaultViewTypeToViewModelTypeResolver( x =>
                                                                     {
                                                                         var viewName = x.FullName;
                                                                         viewName = viewName.Replace( ".Views.", ".ViewModels." );
                                                                         var viewAssemblyName = x.GetTypeInfo().Assembly.FullName;
                                                                         var suffix = viewName.EndsWith( "View" ) ? "Model" : "ViewModel";
                                                                         var viewModelName = string.Format( CultureInfo.InvariantCulture, "{0}{1}, {2}", viewName, suffix, viewAssemblyName );
                                                                         return Type.GetType( viewModelName );
                                                                     } );
ViewModelLocationProvider.SetDefaultViewModelFactory( type => Container.Resolve( type ) );

...and put breakpoints there to see exactly what's the problem. Alternatively, dig into your XamlParseException's InnerExceptions... at about the third level you should find the real problem. But I find my breakpoint-approach more convenient.