App.xaml.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Security.Principal;
using System.Windows;
using System.Windows.Threading;
using Wpf.Ui.Controls;
using MultiTools.Pages;

namespace MultiTools
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App
    {

        private static readonly IHost _host = Host
            .CreateDefaultBuilder()
            .ConfigureAppConfiguration(c => { c.SetBasePath(Path.GetDirectoryName(Assembly.GetEntryAssembly()!.Location)); })
            .ConfigureServices((context, services) =>
            {
                services.AddTransient<DashWindow>();
                services.AddTransient<InstallationWindow>();
                services.AddTransient<MainWindow>();
                services.AddSingleton<NavigationView>();
            }).Build();

        /// <summary>
        /// Gets registered service.
        /// </summary>
        /// <typeparam name="T">Type of the service to get.</typeparam>
        /// <returns>Instance of the service or <see langword="null"/>.</returns>
        public static T GetService<T>()
            where T : class
        {
            return _host.Services.GetService(typeof(T)) as T;
        }

        /// <summary>
        /// Occurs when the application is loading.
        /// </summary>
        private void OnStartup(object sender, StartupEventArgs e)
        {

            _host.Start();
            var mainWindow = _host.Services.GetRequiredService<MainWindow>();
            mainWindow.Show();
        }

        /// <summary>
        /// Occurs when the application is closing.
        /// </summary>
        private async void OnExit(object sender, ExitEventArgs e)
        {
            await _host.StopAsync();

            _host.Dispose();
        }

        /// <summary>
        /// Occurs when an exception is thrown by an application but not handled.
        /// </summary>
        private void OnDispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
        {
            // For more info see https://docs.microsoft.com/en-us/dotnet/api/system.windows.application.dispatcherunhandledexception?view=windowsdesktop-6.0
        }

    }
}