ModernWpfPlayground/App/App.xaml.cs

using System.Windows;
using Prism.Ioc;

namespace ModernWpfPlayground
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App
    {
        protected override void RegisterTypes(IContainerRegistry containerRegistry)
        {
            containerRegistry.Register<MainWindow>();
            containerRegistry.Register<MainWindowViewModel>();
        }

        protected override Window CreateShell()
        {
            return Container.Resolve<MainWindow>();
        }
    }
}