private void MAddUserKeysButton_Click(object sender, RoutedEventArgs e)
        {
            ShowKeys w = new ShowKeys();

            w.Closed += (s, args) => viewModel.PerformValidation();
            w.Show();
        }
        private void MShowKeysButton_Click(object sender, RoutedEventArgs e)
        {
            var window = new ShowKeys();

            window.Closed += (o, ev) => this.viewModel.PerformValidation();
            window.Show();
        }