private void button1_Click(object sender, EventArgs e)
 {
     if (libraryApp.Return(Convert.ToInt32(lblBorrow.Text)))
     {
         MessageBox.Show(string.Format("Return Success: \n{0}", libraryApp.BorrowHistory(Convert.ToInt32(lblBorrow.Text))));
     }
     else
     {
         MessageBox.Show("One or more field haven't been filled correctly");
     }
 }