private void clickAdd(object sender, RoutedEventArgs e)
        {
            var    item      = ((Button)sender).DataContext;
            var    itemIndex = userList.Items.IndexOf(item);
            string candidate = users[itemIndex];
            bool   result    = controller.addNewFriend(username, candidate);
            string msg       = "Adding " + candidate + " to friends list";

            if (!result)
            {
                Utils.Instance.errorAndExit("Error trying to access users records");
            }
            bindNonUserList();
            MessageBox.Show(msg + " succeed");
        }