show steps

         int amount = int.Parse(this.userName.Text);
            this.textBox1.Text = "";
            string current = "";
            do
            {
                int digitCode = '0' + amount % 10;
                char digit = Convert.ToChar(digitCode);//转化为Char
                current = digit + current;//Char相加
                this.textBox1.Text += current + "\r\n";//输出
                amount /= 10;
            } while (amount != 0);
        }