protected void btnDel_Click(object sender, EventArgs e) { int id; try { id = int.Parse(idDel.Value); } catch { SystemClass objSystemClass = new SystemClass(); objSystemClass.addMessage("Có lỗi xảy ra!"); return; } if (id != 0) { objContact.delData(id); } else { SystemClass objSystemClass = new SystemClass(); objSystemClass.addMessage("Có lỗi xảy ra!"); return; } }