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");            }