CalculatorAvalonia/ViewModels/MainWindowViewModel.cs

using Avalonia.Controls;
using CalculatorSuperNew.Views;
using ReactiveUI;

namespace CalculatorSuperNew.ViewModels
{
    public class MainWindowViewModel : ViewModelBase
    {
        UserControl us = new LoginPage();

        public UserControl US { get => us; set => this.RaiseAndSetIfChanged(ref us, value); }

        public LoginPageViewModel loginPage = new LoginPageViewModel();
        public LoginPageViewModel LP { get => loginPage; set => loginPage = value; }

        public CalculatorViewModel calculator = new CalculatorViewModel();
        public CalculatorViewModel CP { get => calculator; set => calculator = value; }

        public void toCalculator()
        {
            if(LP.LogIn())
            {
                US = new Calculator();
            }
        }

    }
}