NullReferenceException on DisplayRootViewFor<>

Question

I've created a class derived from BootstrapperBase, overwrote OnStartup() and call DisplayRootViewFor<AppViewModel>() just like in the documentation.

But when i start the app, i get a NullReferenceException on DisplayRooViewFor<AppViewModel>()

using Caliburn.Micro;
using MHBRestore.Logic;
using MHBRestore.UI.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace MHBRestore.UI
{
public class AppBootstrapper : BootstrapperBase
{
    private SimpleContainer _container = new SimpleContainer();

    public AppBootstrapper()
    {
        Initialize();
    }

    protected override void OnStartup(object sender, StartupEventArgs e)
    {
        DisplayRootViewFor<AppViewModel>();
    }

    protected override object GetInstance(Type service, string key)
    {
        return _container.GetInstance(service, key);
    }

    protected override IEnumerable<object> GetAllInstances(Type service)
    {
        return _container.GetAllInstances(service);
    }

    protected override void BuildUp(object instance)
    {
        _container.BuildUp(instance);
    }
}
}

score 0 · Accepted Answer · answered Jun 05 '17 at 15:29

Try to override the Configure method and register your view model type:

public class AppBootstrapper : BootstrapperBase
{
    private SimpleContainer _container = new SimpleContainer();

    public AppBootstrapper()
    {
        Initialize();
    }

    protected override void Configure()
    {
        _container.Singleton<IWindowManager, WindowManager>();
        _container.Singleton<IEventAggregator, EventAggregator>();
        _container.RegisterPerRequest(typeof(AppViewModel), null, typeof(AppViewModel));
    }

    protected override void OnStartup(object sender, StartupEventArgs e)
    {
        DisplayRootViewFor<AppViewModel>();
    }

    protected override object GetInstance(Type service, string key)
    {
        return _container.GetInstance(service, key);
    }

    protected override IEnumerable<object> GetAllInstances(Type service)
    {
        return _container.GetAllInstances(service);
    }

    protected override void BuildUp(object instance)
    {
        _container.BuildUp(instance);
    }
}

NullReferenceException on DisplayRootViewFor<>

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