private void btnNewUser_Click(object sender, RoutedEventArgs e)
        {
            FormUser form = new FormUser(context);

            form.ShowDialog();
            userViewSource.View.Refresh();
        }
        private void btnUpdateUser_Click(object sender, RoutedEventArgs e)
        {
            user     user = userViewSource.View.CurrentItem as user;
            FormUser form = new FormUser(user, context);

            form.ShowDialog();
            userViewSource.View.Refresh();
        }