private void btDelete_Click(object sender, EventArgs e) { int i = lbTopic.SelectedIndex; if (i == -1) { MessageBox.Show("Select a topic to change"); return; } else { string topicID = topicList[lbTopic.SelectedIndex].TopicID; BOTopic bot = new BOTopic(); bool success = bot.Delete(topicID); if (success) { MessageBox.Show("Delete topic success!"); loadTopicList(); } else MessageBox.Show("Failed to delete a topic!"); txtTopicID.Clear(); txtTopicName.Clear(); btUpdate.Enabled = false; btDelete.Enabled = false; loadTopicList(); } }