---

 public partial class MainWindow : Window
 {
     public MainWindow()
     {
         InitializeComponent();
     }

     private void LoginButton_Click(object sender, RoutedEventArgs e)
     {
         var login = LoginTextBox.Text;
         var password = PasswordTextBox.Password;
         var db = new _6767Context();
         var result = db.Users.Where(x => x.Login == login && x.Password == password).FirstOrDefault();

         if (result != null)
         {
             MainUser.user = result;
             new ListProductWindow().Show();
             Close();
         }
         else
         {
             MessageBox.Show("Введён неверный логин или пароль", "Ошибка", MessageBoxButton.OK, MessageBoxImage.Error);
         }
     }

     private void GuestButton_Click(object sender, RoutedEventArgs e)
     {
         new ListProductWindow().Show();
         Close();
     }