splitter/Splitter-UI/App.axaml.cs

using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using Microsoft.Extensions.DependencyInjection;
using Splitter_UI.Views;

namespace Splitter_UI;

public partial class App : Application
{
    private readonly ServiceProvider _provider = null!;

    public App() { }

    public App(ServiceProvider provider)
    {
        _provider = provider;
    }

    public override void Initialize()
    {
        AvaloniaXamlLoader.Load(this);
    }

    public override void OnFrameworkInitializationCompleted()
    {
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            var vm = _provider.GetRequiredService<MainViewModel>();

            desktop.MainWindow = new MainWindow
            {
                DataContext = vm
            };
        }

        base.OnFrameworkInitializationCompleted();
    }
}