使用checked关键字处理“溢出”错误

 byte by1, by2;
            if (byte.TryParse(textBox1.Text, out by1) && byte.TryParse(textBox2.Text, out by2)) //判断是否是 Byte类型
            {
                try
                {
                    checked
                    {
                        by1 += by2;
                        textBox3.Text = by1.ToString();
                    }
                }
                catch (OverflowException ex) //溢出异常
                {
                    MessageBox.Show(ex.Message);
                }
            }
            else
            {
                MessageBox.Show("对不起！您输入的数字有问题！请从新输入");
            }