asp.net 日期转换为大写汉字

//年份转换为大写汉字
        public static string numtoUpper(int num)
         {
             return "零壹贰叁肆伍陆柒捌玖"[num].ToString();
         }

//月份转换大写汉字
        public static string monthtoUpper(int month)
        {
            if (month < 10)
            {
                return numtoUpper(month);
            }
            else
            {
                if (month == 10) { return "壹拾"; }

                else
                {
                    return "壹拾" + numtoUpper(month - 10);
                }
            }
        }


//日期转化为大写汉字
        public static string daytoUpper(int day)
        {
            if (day < 20)
            {
                return monthtoUpper(day);
            }
            else
            {
                String str = day.ToString();
                if (str[1] == '0')
                {
                    return numtoUpper(Convert.ToInt16(str[0].ToString())) + "拾";
                }
                else
                {
                    return numtoUpper(Convert.ToInt16(str[0].ToString())) + "拾"
                        + numtoUpper(Convert.ToInt16(str[1].ToString()));
                }
            }
        }

static void Main(string[] args)
        {
            string year = "2013";
            string retur = string.Empty;
            for (int i = 0; i < year.Length; i++)
            {
                retur += numtoUpper(int.Parse(year[i].ToString())).ToString();
            }
            Console.WriteLine(retur + "  年");
            retur = string.Empty;
            string month = "12";
            retur = monthtoUpper(Convert.ToInt32(month));
            Console.WriteLine(retur + "  月");
            string day = "31";
            retur = daytoUpper(Convert.ToInt32(day));
            Console.WriteLine(retur + "  日");
            Console.ReadLine();
        }