private void button1_Click(object sender, EventArgs e) { if (string.IsNullOrEmpty(txtTitle.Text) || Convert.ToInt32(lblID.Text) <= 0) { MessageBox.Show("One or more field haven't been filled correctly"); return; } if (libraryApp.UpdateBook(Convert.ToInt32(lblID.Text), txtTitle.Text.Trim(), txtAuthor.Text.Trim(), txtPublisher.Text.Trim(), dtpPublished.Value)) { MessageBox.Show("Update Success"); } else { MessageBox.Show("Error occurred\n Please relogin if the error continues!"); } }