declaratrions-automatization/DeclarationAutomatization/App.xaml.cs

using System.Windows;
using DeclarationAutomatization.Services;
using DeclarationAutomatization.ViewModels;
using DeclarationAutomatization.Views;
using Microsoft.Extensions.DependencyInjection;

namespace DeclarationAutomatization;

public partial class App : Application
{
    private ServiceProvider? _serviceProvider;

    private void OnStartup(object sender, StartupEventArgs e)
    {
        var services = new ServiceCollection();
        ConfigureServices(services);
        _serviceProvider = services.BuildServiceProvider();

        var mainWindow = _serviceProvider.GetRequiredService<MainWindow>();
        mainWindow.Show();
    }

    private static void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<Sheet1ImportService>();
        services.AddSingleton<ExcelImportService>();
        services.AddSingleton<CodesImportService>();
        services.AddSingleton<TransformService>();
        services.AddSingleton<RulesPersistenceService>();
        services.AddSingleton<CodeLookupService>();
        services.AddSingleton<Sheet3ExpandService>();
        services.AddSingleton<ExcelExportService>();
        services.AddSingleton<MainViewModel>();
        services.AddSingleton<MainWindow>();
    }

    protected override void OnExit(ExitEventArgs e)
    {
        _serviceProvider?.Dispose();
        base.OnExit(e);
    }
}