R29/WpfApp29/ViewModels/UserWindowViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using WpfApp29.Pages;

namespace WpfApp29.ViewModels
{
    internal class UserWindowViewModel
    {
        public UserWindowViewModel()
        {
            AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Navigate(MainPage);
        }
        private MainPage? _mainPage;
        private AccountPage? _accountPage;
        private UserListPage? _userListPage;
        public MainPage MainPage
        {
            get => _mainPage ??= new MainPage();
        }
        public AccountPage AccountPage
        {
            get => _accountPage ??= new AccountPage();
        }
        public UserListPage UserListPage
        {
            get => _userListPage ??= new UserListPage();
        }

        public RelayCommand? _commandGoMainMenu;
        public RelayCommand CommandGoMainMenu
        {
            get
            {
                return _commandGoMainMenu ??= new RelayCommand(
                x =>
                {
                    AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Navigate(MainPage);
                },
                x =>
                {
                    if (AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Content is MainPage)
                    {
                        return false;
                    }
                    return true;
                }
                );
            }
        }
        public RelayCommand? _commandGoAccount;
        public RelayCommand CommandGoAccount
        {
            get
            {
                return _commandGoAccount ??= new RelayCommand(
                x =>
                {
                    AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Navigate(AccountPage);
                },
                x =>
                {
                    if (AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Content is AccountPage)
                    {
                        return false;
                    }
                    return true;
                }
                );
            }
        }
        public RelayCommand? _commandGoUserList;
        public RelayCommand CommandGoUserList
        {
            get
            {
                return _commandGoUserList ??= new RelayCommand(
                x =>
                {
                    AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Navigate(UserListPage);
                },
                x =>
                {
                    if (AppHelper.GetWindowAtType<UserWindow>()?.FramePages.Content is UserListPage)
                    {
                        return false;
                    }
                    return true;
                }
                );
            }
        }
        public RelayCommand? _commandGoExit;
        public RelayCommand CommandGoExit
        {
            get
            {
                return _commandGoExit ??= new RelayCommand(
                x =>
                {
                    new MainWindow().Show();
                    AppHelper.GetWindowAtType<UserWindow>()?.Close();
                }
                );
            }
        }
    }
}