金额小写转中文大写类

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


namespace Class_ZhH
{
    /// <summary>
    /// 金额小写转中文大写类(附带一个数字转大写)。
    /// 整数支持到万亿；小数部分支持到分(超过两位将进行Banker舍入法处理)
    /// </summary>
    public class NumGetString
    {
        private static String[] Ls_ShZ ={ "零", "壹", "贰", "叁", "肆", "伍", "陆", "柒", "捌", "玖", "拾" };
        private static String[] Ls_DW_Zh ={ "元", "拾", "佰", "仟", "万", "拾", "佰", "仟", "亿", "拾", "佰", "仟", "万" };
        private static String[] Num_DW ={ "","拾", "佰", "仟", "万", "拾", "佰", "仟", "亿", "拾", "佰", "仟", "万" };
        private static String[] Ls_DW_X ={ "角", "分" };

        /// <summary>
        /// 金额小写转中文大写。
        /// 整数支持到万亿；小数部分支持到分(超过两位将进行Banker舍入法处理)
        /// </summary>
        /// <param name="Num">需要转换的双精度浮点数</param>
        /// <returns>转换后的字符串</returns>
        public static String NumGetStr(Double Num)
        {
            Boolean iXSh_bool = false;//是否含有小数，默认没有(0则视为没有)
            Boolean iZhSh_bool = true;//是否含有整数,默认有(0则视为没有)

            string NumStr;//整个数字字符串
            string NumStr_Zh;//整数部分
            string NumSr_X = "";//小数部分
            string NumStr_DQ;//当前的数字字符
            string NumStr_R = "";//返回的字符串

            Num = Math.Round(Num, 2);//四舍五入取两位

            //各种非正常情况处理
            if (Num < 0)
                return "不转换欠条";
            if (Num > 9999999999999.99)
                return "很难想象谁会有这么多钱！";
            if (Num == 0)
                return Ls_ShZ[0];

            //判断是否有整数
            if (Num < 1.00)
                iZhSh_bool = false;

            NumStr = Num.ToString();

            NumStr_Zh = NumStr;//默认只有整数部分
            if (NumStr_Zh.Contains("."))
            {//分开整数与小数处理
                NumStr_Zh = NumStr.Substring(0, NumStr.IndexOf("."));
                NumSr_X = NumStr.Substring((NumStr.IndexOf(".") + 1), (NumStr.Length - NumStr.IndexOf(".") - 1));
                iXSh_bool = true;
            }


            if (NumSr_X == "" || int.Parse(NumSr_X) <= 0)
            {//判断是否含有小数部分
                iXSh_bool = false;
            }

            if (iZhSh_bool)
            {//整数部分处理
                NumStr_Zh = Reversion_Str(NumStr_Zh);//反转字符串

                for (int a = 0; a < NumStr_Zh.Length; a++)
                {//整数部分转换
                    NumStr_DQ = NumStr_Zh.Substring(a, 1);
                    if (int.Parse(NumStr_DQ) != 0)
                        NumStr_R = Ls_ShZ[int.Parse(NumStr_DQ)] + Ls_DW_Zh[a] + NumStr_R;
                    else if (a == 0 || a == 4 || a == 8)
                    {
                        if (NumStr_Zh.Length > 8 && a == 4)
                            continue;
                        NumStr_R = Ls_DW_Zh[a] + NumStr_R;
                    }
                    else if (int.Parse(NumStr_Zh.Substring(a - 1, 1)) != 0)
                        NumStr_R = Ls_ShZ[int.Parse(NumStr_DQ)] + NumStr_R;

                }

                if (!iXSh_bool)
                    return NumStr_R + "整";

                //NumStr_R += "零";
            }

            for (int b = 0; b < NumSr_X.Length; b++)
            {//小数部分转换
                NumStr_DQ = NumSr_X.Substring(b, 1);
                if (int.Parse(NumStr_DQ) != 0)
                    NumStr_R += Ls_ShZ[int.Parse(NumStr_DQ)] + Ls_DW_X[b];
                else if (b != 1 && iZhSh_bool)
                    NumStr_R += Ls_ShZ[int.Parse(NumStr_DQ)];
            }

            return NumStr_R;

        }

        /// <summary>
        /// 提供一个数字直接转大写（即不带单位）
        /// </summary>
        /// <param name="NumStr">需要转换的数字字符串</param>
        /// <param name="Dw">是否带单位</param>
        /// <returns>转换后的字符串</returns>
        public static String LowercaseGetCap(String NumStr,Boolean Dw)
        {
            String CapStr="";
            String NumStr_LS;

            if (NumStr == String.Empty)
                return String.Empty;

            if (Dw)
                NumStr = Reversion_Str(NumStr);

            try
            {
                for (Int32 c = 0; c < NumStr.Length; c++)
                {
                    NumStr_LS = NumStr.Substring(c, 1);
                    if (Dw)
                    {
                        if (int.Parse(NumStr_LS) != 0)
                            CapStr = Ls_ShZ[int.Parse(NumStr_LS)] + Num_DW[c] + CapStr;
                        else if (c == 0 || c == 4 || c == 8)
                        {
                            if (NumStr_LS.Length > 8 && c == 4)
                                continue;
                            CapStr = Num_DW[c] + CapStr;
                        }
                        else if (int.Parse(NumStr.Substring(c - 1, 1)) != 0)
                            CapStr = Ls_ShZ[int.Parse(NumStr_LS)] + CapStr;
                    }
                    else
                        CapStr += Ls_ShZ[int.Parse(NumStr_LS)];
                }

                return CapStr;
            }
            catch (Exception Err)
            {
                return "转换错误！"+Err.Message;
            }
        }

        /// <summary>
        /// 反转字符串
        /// </summary>
        /// <param name="Rstr">需要反转的字符串</param>
        /// <returns>反转后的字符串</returns>
        private static String Reversion_Str(String Rstr)
        {
            Char[] LS_Str = Rstr.ToCharArray();
            Array.Reverse(LS_Str);
            String ReturnSte = "";
            ReturnSte = new String(LS_Str);//反转字符串

            return ReturnSte;
        }
    }
}

DEMO:

 private void btn_Ok_Click(object sender, EventArgs e)
        {
            Double iNum = 0.0;
            if (Double.TryParse(txt_Num.Text, out iNum) == false)
            {
                txt_Num.Focus();
                txt_Num.SelectAll();
                MessageBox.Show("非法的金额数字");
                return;
            }

            txt_Ret.Text = NumGetString.NumGetStr(iNum);
        }