MyAvaloniaDemo/ViewModels/AppViewModel.cs

using System;
using ReactiveUI;

namespace MyAvaloniaApp.ViewModels;

/// <summary>
/// 应用程序级别的 ViewModel，实现 IScreen 接口
/// </summary>
public class AppViewModel : ReactiveObject, IScreen
{
    public RoutingState Router { get; }

    public MainWindowViewModel MainWindowViewModel { get; }

    public AppViewModel()
    {
        Router = new RoutingState();
        // 先创建 MainWindowViewModel，传入自身作为 IScreen
        MainWindowViewModel = new MainWindowViewModel(this);
    }
}