new/ViewModels/MainWindowViewModel.cs

using YtYtAvalonia.Models;
using YtYtAvalonia.Views;
using YtYtAvalonia.ViewModels;

using Avalonia.Controls;
using ReactiveUI;
using YtYtAvalonia.View;

namespace YtYtAvalonia.ViewModels
{
    public class MainWindowViewModel : ViewModelBase
    {
#pragma warning disable CA1822 // Mark members as static

        public static SuharevaContext myConnection = new SuharevaContext();

        RegistrationViewModel regPage = new RegistrationViewModel(myConnection);
        public RegistrationViewModel RegPage { get => regPage; set => regPage = value; }

#pragma warning restore CA1822 // Mark members as static
        public string Greeting => "Welcome to Avalonia!";

        public UserControl UC { get => uc; set => this.RaiseAndSetIfChanged(ref uc, value); }
#pragma warning restore CA1822 // Mark members as static

        private UserControl uc = new LoginView();

        public void LoadRegistrationView() => UC = new RegistrationView();
    }
}