private void changeButton_Click(object sender, RoutedEventArgs e)
        {
            DataRowView row = (DataRowView)dataGrid.Items.CurrentItem;

            int itemID = Convert.ToInt32(row[0]);
            SubscriptionsAdd subscriptionsWindow = new SubscriptionsAdd(false, row);

            subscriptionsWindow.ShowDialog();
        }
        private void addButton_Click(object sender, RoutedEventArgs e)
        {
            SubscriptionsAdd subscriptionsWindow = new SubscriptionsAdd(true);

            subscriptionsWindow.ShowDialog();
        }