КИ Лаб3 C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Lab3
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            List<Product> list = Data.GetProducts();
            lstBox.ItemsSource = list;
        }

        private void btn1_Click(object sender, RoutedEventArgs e)
        {

            if (lstBox.SelectedIndex == -1)
            {
            MessageBox.Show("You must select an item!", "Error");
            return;
            }

            var newWindow = new Details()
            {
            DataContext = lstBox.SelectedItem as Product
            };


            newWindow.Show();

        }
    }
}