private void Button_Click_2(object sender, RoutedEventArgs e)
        {
            Wybor wybor = new Wybor();

            wybor.Show();
            this.Close();
        }
 private void Button_Click(object sender, RoutedEventArgs e)
 {
     if (SystemCafe.CashierInstance.Login(LoginTxt.Text, PasswordTxt.Password) == true)
     {
         SystemCafe.Instance.AddLoggedCashier(LoginTxt.Text, PasswordTxt.Password);
         WyborKasjer wyborKasjer = new WyborKasjer();
         wyborKasjer.Show();
         this.Close();
     }
     else if (SystemCafe.SystemInstance.Login(LoginTxt.Text, PasswordTxt.Password) == true)
     {
         SystemCafe.Instance.AddLoggedManager(LoginTxt.Text, PasswordTxt.Password);
         Wybor window = new Wybor();
         window.Show();
         this.Close();
     }
     else
     {
         MessageBox.Show("Błędne dane");
     }
 }