AutoCatAvalonia/AutoCat/Views/AuthWindow.axaml.cs

using AutoCat.ViewModels;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.ApplicationLifetimes;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting.Internal;

namespace AutoCat.Views;

public partial class AuthWindow : Window
{
    public AuthWindow()
    {
        InitializeComponent();

        if (DataContext is AuthWindowViewModel vm)
        {
            vm.ReplaceWithMainWindowEvent += (sender, args) =>
            {
                if (Application.Current is not App app) return;
                if (app.ApplicationLifetime is not IClassicDesktopStyleApplicationLifetime desktop) return;
                
                var mainWindow = app.AppHost.Services.GetRequiredService<MainWindow>();
                mainWindow.Show();
                desktop.MainWindow = mainWindow;
                Close();
            };
        }
    }
}