Learn-WinUI-3-Second-Edition/Chapter03/Complete/MyMediaCollection/App.xaml.cs

using Microsoft.UI.Xaml;
using MyMediaCollection.ViewModels;

namespace MyMediaCollection
{
    /// <summary>
    /// Provides application-specific behavior to supplement the default Application class.
    /// </summary>
    public partial class App : Application
    {
        /// <summary>
        /// Initializes the singleton application object.  This is the first line of authored code
        /// executed, and as such is the logical equivalent of main() or WinMain().
        /// </summary>
        public App()
        {
            this.InitializeComponent();
        }

        public static MainViewModel ViewModel { get; } = new MainViewModel();

        /// <summary>
        /// Invoked when the application is launched.
        /// </summary>
        /// <param name="args">Details about the launch request and process.</param>
        protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
        {
            m_window = new MainWindow();
            m_window.Activate();
        }

        private Window m_window;
    }
}