crosslangdevstudio/Views/MainWindow.axaml.cs

using System.Threading;
using System.Threading.Tasks;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Platform.Storage;
using Avalonia.Threading;
using CommunityToolkit.Mvvm.Messaging;
using CrossLangDevStudio.Messages;
using CrossLangDevStudio.ViewModels;
using MsBox.Avalonia;
using MsBox.Avalonia.Enums;
using Tabalonia.Controls;

namespace CrossLangDevStudio.Views;

public partial class MainWindow : Window
{
    private async Task CloseWindowAsync(WindowClosingEventArgs e, MainWindowViewModel vm)
    {
        var box = MessageBoxManager
              .GetMessageBoxStandard("Save?", $"You have unsaved work do you want to save?",
                          ButtonEnum.YesNoCancel, MsBox.Avalonia.Enums.Icon.Question);
       
            switch (await box.ShowWindowDialogAsync(this))
            {
                case ButtonResult.Yes:
                    vm.SaveAll();
                    break;
                case ButtonResult.Cancel:
                    e.Cancel = true;
                    break;
            }
        
    }
    public MainWindow()
    {
        InitializeComponent();

        if (Design.IsDesignMode)
            return;
        this.Closing += (sender, e) =>
        {
            if (this.DataContext is MainWindowViewModel vm)
            {
                if (vm.HasUnsaved)
                {
                    //thanks https://github.com/AvaloniaUI/Avalonia/issues/4810#issuecomment-704372304
                    using (var source = new CancellationTokenSource())
                    {
                        CloseWindowAsync(e, vm).ContinueWith(e => source.Cancel(), TaskScheduler.FromCurrentSynchronizationContext());
                        Dispatcher.UIThread.MainLoop(source.Token);
                    }
                }
            }
        };


        // Whenever 'Send(new PurchaseAlbumMessage())' is called, invoke this callback on the MainWindow instance:
        WeakReferenceMessenger.Default.Register<MainWindow, NewProjectMessage>(this, static (w, m) =>
            {
                // Create an instance of MusicStoreWindow and set MusicStoreViewModel as its DataContext.
                var dialog = new NewProjectDialog
                {
                    DataContext = new NewProjectDialogViewModel()
                };
                // Show dialog window and reply with returned AlbumViewModel or null when the dialog is closed.
                m.Reply(dialog.ShowDialog<string?>(w));

            });
        WeakReferenceMessenger.Default.Register<MainWindow, InstallPackageMessage>(this, static (w, m) =>
        {
            var dialog = new InstallPackageDialog
            {
                DataContext = new InstallPackageDialogViewModel(m)
            };

            m.Reply(dialog.ShowDialog<CrossLangVersion?>(w));
        });
        WeakReferenceMessenger.Default.Register<MainWindow, GetWindowMessage>(this, static (w, m) =>
            {
                m.Reply(w);
            }
        );
        WeakReferenceMessenger.Default.Register<MainWindow, PublishMessage>(this, static (w, m) =>
        {
            var dialog = new PublishDialogView
            {
                DataContext = new PublishDialogViewModel(m.Path)
            };
            m.Reply(dialog.ShowDialog(w));
        });
    }
}