presence/Presence.Desktop/ViewModels/MainWindowViewModels.cs

using System;
using Microsoft.Extensions.DependencyInjection;
using ReactiveUI;

namespace Presence.Desktop.ViewModels;

// public class MainWindowViewModel: ViewModelBase, IScreen
// {
//     public RoutingState Router { get; } = new RoutingState();

//     public MainWindowViewModel(IServiceProvider serviceProvider)
//     {
//         var groupViewModel = serviceProvider.GetRequiredService<GroupViewModel>();
//         Router.Navigate.Execute(groupViewModel);
//     }
// }

public class MainWindowViewModel : ViewModelBase, IScreen
{
    public RoutingState Router { get; } = new RoutingState();

    public MainWindowViewModel(IServiceProvider serviceProvider)
    {
        var startViewModel = new StartViewModel(this);
        Router.Navigate.Execute(startViewModel);
    }
}