sa/Stars Assistant/ViewModels/MainWindowViewModel.cs

using System.Collections.ObjectModel;
using System.Reactive.Disposables;
using System.Reactive.Linq;
using ReactiveUI;
using ReactiveUI.SourceGenerators;

namespace StarsAssistant.ViewModels;

public partial class MainWindowViewModel : ViewModelBase, IActivatableViewModel
{
    public ViewModelActivator Activator { get; } = new ViewModelActivator();

    [ObservableAsProperty]
    private string _welcomeMessage;

    public MainWindowViewModel()
    {
        _welcomeMessage = "Lorem Ipsum";
        _welcomeMessageHelper = Observable.Return("Dolor sit amet")
            .ToProperty(this, x => x.WelcomeMessage);

        this.WhenActivated((CompositeDisposable disposables) => 
        {
            // /* handle activation */
            // Disposable
            //     .Create(() => { /* handle deactivation */ })
            //     .DisposeWith(disposables);
        });
    }        

    public ObservableCollection<PlanetViewModel> Planets { get; } = PlanetViewModel.LoadAll();

}