格式化为中文数字

namespace Microshaoft
{
    using System;

    public class ChineseFormat : System.ICustomFormatter, System.IFormatProvider
    {
        //如果format Type与当前实例类型相同，则为当前实例，否则为空引用 
        public object GetFormat(Type format)
        {
            if (format == typeof (ICustomFormatter))
            {
                return this;
            }
            return null;
        }

        //实现Format方法说明: 
        //如果您的格式方法不支持格式，则确定正在设置格式的对象是否实现 IFormattable 接口。 
        //如果实现，请调用该接口的IFormattable.ToString 方法。 
        //否则，调用基础对象的默认 Object.ToString 方法。 
        public string Format(string format, object arg, IFormatProvider provider)
        {
            if (format == null)
            {
                if (arg is IFormattable)
                {
                    return ((IFormattable) arg).ToString(format, provider);
                }
                return arg.ToString();
            }
            else
            {
                if (format == "ChineseFormat")
                {
                    string[] Nums = new string[] {"零", "壹", "贰", "叁", "肆", "伍", "陆", "柒", "捌", "玖"};
                    //位 数组 
                    string[] Digits = new string[] {"", "拾", "佰", "仟"};
                    //单位 数组 
                    string[] Units = new string[] {"", "[万]", "[亿]", "[万亿]"};
                    return ConvertNumberToChinese(arg.ToString(), Nums, Digits, Units);
                    //return "***"+arg.ToString(); 
                }
                else
                {
                    if (arg is IFormattable)
                    {
                        return ((IFormattable) arg).ToString(format, provider);
                    }
                    return arg.ToString();
                }
            }
        }

        public static string ConvertNumberToChinese(string x, string[] Nums, string[] Digits, string[] Units)
        {
            string S = ""; //返回值 
            int p = 0; //字符位置指针 
            int m = x.Length % 4; //取模 

            // 四位一组得到组数 
            int k = (m > 0 ? x.Length / 4 + 1 : x.Length / 4);

            // 外层循环在所有组中循环 
            // 从左到右 高位到低位 四位一组 逐组处理 
            // 每组最后加上一个单位: "[万亿]","[亿]","[万]" 
            for (int i = k; i > 0; i--)
            {
                int L = 4;
                if (i == k && m != 0)
                {
                    L = m;
                }
                // 得到一组四位数 最高位组有可能不足四位 
                string s = x.Substring(p, L);
                int l = s.Length;

                // 内层循环在该组中的每一位数上循环 从左到右 高位到低位 
                for (int j = 0; j < l; j++)
                {
                    //处理改组中的每一位数加上所在位: "仟","佰","拾",""(个) 
                    int n = Convert.ToInt32(s.Substring(j, 1));
                    if (n == 0)
                    {
                        if (j < l - 1
                            && Convert.ToInt32(s.Substring(j + 1, 1)) > 0 //后一位(右低) 
                            && !S.EndsWith(Nums[n]))
                        {
                            S += Nums[n];
                        }
                    }
                    else
                    {
                        //处理 1013 一千零"十三", 1113 一千一百"一十三" 
                        if (!(n == 1 && (S.EndsWith(Nums[0]) | S.Length == 0) && j == l - 2))
                        {
                            S += Nums[n];
                        }
                        S += Digits[l - j - 1];
                    }
                }
                p += L;
                // 每组最后加上一个单位: [万],[亿] 等 
                if (i < k) //不是最高位的一组 
                {
                    if (Convert.ToInt32(s) != 0)
                    {
                        //如果所有 4 位不全是 0 则加上单位 [万],[亿] 等 
                        S += Units[i - 1];
                    }
                }
                else
                {
                    //处理最高位的一组,最后必须加上单位 
                    S += Units[i - 1];
                }
            }
            return S;
        }
    }
}

namespace Test
{
    using System;
    using Microshaoft;

    class AppTest
    {
        static void Main()
        {
            string printString = String.Empty;
            long i = 1100000013;
            ChineseFormat fmt = new ChineseFormat();

            printString = string.Format(fmt, "显示正常格式: {0}", i);
            Console.WriteLine(printString);
            printString = string.Format(fmt, "显示正常格式: {0:C}", i);
            Console.WriteLine(printString);
            printString = string.Format(fmt, "显示自定义格式: {0:ChineseFormat}", i);
            Console.WriteLine(printString);

            Console.ReadLine();
        }
    }
}