private void button1_Click(object sender, EventArgs e) { if (textBox1.Text == "")//validation part { MessageBox.Show("Please, insert Book ID to delete"); } else { int r = EmC.DeleteBook(Convert.ToInt32(textBox1.Text)); if (r == 0) { MessageBox.Show("Your Request is Invalid"); } else { MessageBox.Show("The Book was Delete Successfully!"); } } }