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");

            }