R29/WpfApp29/ViewModels/MainWindowViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using WpfApp29.Models;

namespace WpfApp29.ViewModels
{
    internal class MainWindowViewModel : BaseViewModel
    {
        public User? _user;
        public User User
        {
            get => _user ??= new User();
            set
            {
                _user = value;
                OnPropertyChanged();
            }
        }
        public RelayCommand? _commandLogin;
        public RelayCommand CommandLogin
        {
            get
            {
                return _commandLogin ??= new RelayCommand(
                x =>
                {
                    User.Password = (x as PasswordBox)?.Password ?? "";
                    MainContext ctx = new MainContext();
                    User? user = ctx.Users.FirstOrDefault(u => u.Login == User.Login && u.Password == User.Password);
                    if (user == null)
                    {
                        MessageBox.Show("Вы ввели неверные логин или пароль");
                        return;
                    }
                    User.CurrentUser = user;
                    new UserWindow().Show();
                    AppHelper.GetWindowAtType<MainWindow>()?.Close();
                }
                );
            }
        }
        public RelayCommand? _commandGoRegister;
        public RelayCommand? CommandGoRegister
        {
            get
            {
                return _commandGoRegister ??= new RelayCommand(
                x =>
                {
                    new RegistrationWindow().Show();
                    AppHelper.GetWindowAtType<MainWindow>()?.Close();
                }
                );
            }
        }

    }
}