小寫數字金額轉換成大寫金額（C#）

using System;
using System.Collections.Generic;
using System.Text;

namespace FrameworkApp
{
    // 該類重載的 ToString() 方法返回的是大寫金額字串
    public class Money
    {
        public string Yuan = "元";                        // “元”，可以改為“圓”、“盧布”之類
        public string Jiao = "角";                        // “角”，可以改為“拾”
        public string Fen = "分";                        // “分”，可以改為“美分”之類
        static string Digit = "零壹貳三肆伍陸柒捌玖";      // 大寫數字
        bool isAllZero = true;                        // 片段內是否全零
        bool isPreZero = true;                        // 低一位元字是否是零
        bool Overflow = false;                       // 溢出標誌
        long money100;                                   // 金額*100，即以“分”為單位的金額
        long value;                                      // money100的絕對值
        StringBuilder sb = new StringBuilder();         // 大寫金額字串，逆序
        // 唯讀屬性: "零元"
        public string ZeroString
        {
            get { return Digit[0] + Yuan; }
        }
        // 建構函式
        public Money(decimal money)
        {
            try { money100 = (long)(money * 100m); }
            catch { Overflow = true; }
            if (money100 == long.MinValue) Overflow = true;
        }
        // 重載 ToString() 方法，返回大寫金額字串
        public override string ToString()
        {
            if (Overflow) return "金額超出範圍";
            if (money100 == 0) return ZeroString;
            string[] Unit = { Yuan, "萬", "億", "萬", "億億" };
            value = System.Math.Abs(money100);
            ParseSection(true);
            for (int i = 0; i < Unit.Length && value > 0; i++)
            {
                if (isPreZero && !isAllZero) sb.Append(Digit[0]);
                if (i == 4 && sb.ToString().EndsWith(Unit[2]))
                    sb.Remove(sb.Length - Unit[2].Length, Unit[2].Length);
                sb.Append(Unit[i]);
                ParseSection(false);
                if ((i % 2) == 1 && isAllZero)
                    sb.Remove(sb.Length - Unit[i].Length, Unit[i].Length);
            }
            if (money100 < 0) sb.Append("負");
            return Reverse();
        }
        // 解析“片段”: “角分(2位)”或“萬以內的一段(4位)”
        void ParseSection(bool isJiaoFen)
        {
            string[] Unit = isJiaoFen ?
              new string[] { Fen, Jiao } :
              new string[] { "", "拾", "佰", "仟" };
            isAllZero = true;
            for (int i = 0; i < Unit.Length && value > 0; i++)
            {
                int d = (int)(value % 10);
                if (d != 0)
                {
                    if (isPreZero && !isAllZero) sb.Append(Digit[0]);
                    sb.AppendFormat("{0}{1}", Unit[i], Digit[d]);
                    isAllZero = false;
                }
                isPreZero = (d == 0);
                value /= 10;
            }
        }
        // 反轉字串
        string Reverse()
        {
            StringBuilder sbReversed = new StringBuilder();
            for (int i = sb.Length - 1; i >= 0; i--)
                sbReversed.Append(sb[i]);
            return sbReversed.ToString();
        }
    }
}