LehrerApp/LehrerApp.Desktop/App.axaml.cs

using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using LehrerApp.Desktop.ViewModels;
using LehrerApp.Desktop.ViewModels.Groups;
using LehrerApp.Desktop.ViewModels.Students;
using LehrerApp.Desktop.Views;
using Microsoft.Extensions.DependencyInjection;

namespace LehrerApp.Desktop;

public class App : Application
{
    public static IServiceProvider Services { get; private set; } = null!;

    public override void Initialize() => AvaloniaXamlLoader.Load(this);

    public override void OnFrameworkInitializationCompleted()
    {
        Services = AppBootstrapper.BuildServices();

        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            var mainVm = Services.GetRequiredService<MainWindowViewModel>();
            WireCallbacks(mainVm);
            desktop.MainWindow = new MainWindow { DataContext = mainVm };
        }

        base.OnFrameworkInitializationCompleted();
    }

    private static void WireCallbacks(MainWindowViewModel main)
    {
        // GroupList → GroupDetail
        var gl = Services.GetRequiredService<GroupListViewModel>();
        gl.OnNavigateToDetail = id => main.NavigateToGroupDetail(id);
        gl.OnAddGroup         = () => ShowAddGroupDialog(gl);

        // Dashboard → GroupDetail (Chips)
        var dash = Services.GetRequiredService<DashboardViewModel>();
        dash.OnNavigateToGroup = id => main.NavigateToGroupDetail(id);

        // StudentList → StudentDetail
        var sl = Services.GetRequiredService<StudentListViewModel>();
        sl.OnNavigateToDetail = id => main.NavigateToStudent(id);
    }

    private static async void ShowAddGroupDialog(GroupListViewModel groupList)
    {
        var vm = new ViewModels.Groups.AddGroupDialogViewModel(
            Services.GetRequiredService<Core.Interfaces.IGroupRepository>(),
            Services.GetRequiredService<Core.Services.SchoolYearService>());
        var dialog = new Views.Groups.AddGroupDialog { DataContext = vm };

        if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime { MainWindow: { } owner })
        {
            var ok = await dialog.ShowDialog<bool>(owner);
            if (ok) groupList.LoadGroups();
        }
    }
}