private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            var person = this.ListBox.SelectedItem as Person;
            if (person == null)
            {
                person = new Person
                    {
                        BirthDate = this.BirthDateTextBox.Text,
                        FirstName = this.FirstNameTextBox.Text,
                        LastName = this.LastNameTextBox.Text
                    };

                this.ListBox.Items.Add(person);
            }
            else
            {
                person.FirstName = this.FirstNameTextBox.Text;
                person.LastName = this.LastNameTextBox.Text;
                person.BirthDate = this.BirthDateTextBox.Text;
            }

            using (var context = new PersonContext())
            {
                context.Persons.AddOrUpdate(person);
                context.SaveChanges();
            }
        }
        public MainWindow()
        {
            InitializeComponent();

            using (var context = new PersonContext())
            {
                var dbSet = context.Persons.ToList();
                foreach (var person in dbSet)
                {
                    this.ListBox.Items.Add(person);
                }
            }
        }