C#数字金额转换大写金额

           /// 转换数字金额主函数（包括小数）
          ///
          /// 数字字符串
          /// 转换成中文大写后的字符串或者出错信息提示字符串
          public string ConvertSum(string str)
          {
               if(!IsPositveDecimal(str))
               return "输入的不是正数字！";
               if(Double.Parse(str)>999999999999.99)
               return "数字太大，无法换算，请输入一万亿元以下的金额";
               char[] ch=new char[1];
               ch[0]='.'; //小数点
               string[] splitstr=null; //定义按小数点分割后的字符串数组
               splitstr=str.Split(ch[0]);//按小数点分割字符串
               if(splitstr.Length==1) //只有整数部分
               return ConvertData(str)+"圆整";
               else //有小数部分
               {
                    string rstr;
                    rstr=ConvertData(splitstr[0])+"圆";//转换整数部分
                    rstr+=ConvertXiaoShu(splitstr[1]);//转换小数部分
                    return rstr;
               }
          }
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          ///
          /// 转换数字（整数）
          ///
          /// 需要转换的整数数字字符串
          /// 转换成中文大写后的字符串
          public string ConvertData(string str)
          {
               string tmpstr="";
               string rstr="";
               int strlen=str.Length;
               if (strlen<=4)//数字长度小于四位
               {
                    rstr= ConvertDigit(str);

               }
               else
               {
                    if (strlen<=8)//数字长度大于四位，小于八位
                    {
                         tmpstr=str.Substring(strlen-4,4);//先截取最后四位数字
                         rstr=ConvertDigit(tmpstr);//转换最后四位数字
                         tmpstr=str.Substring(0,strlen-4);//截取其余数字
                         //将两次转换的数字加上萬后相连接
                         rstr= String.Concat(ConvertDigit(tmpstr)+"萬",rstr);
                         rstr=rstr.Replace("零零","零");
                    }
                else
                if(strlen<=12)//数字长度大于八位，小于十二位
                {
                     tmpstr=str.Substring(strlen-4,4);//先截取最后四位数字
                     rstr=ConvertDigit(tmpstr);//转换最后四位数字
                     tmpstr=str.Substring(strlen-8,4);//再截取四位数字
                     rstr= String.Concat(ConvertDigit(tmpstr)+"萬",rstr);
                     tmpstr=str.Substring(0,strlen-8);
                     rstr= String.Concat(ConvertDigit(tmpstr)+"億",rstr);
                     rstr=rstr.Replace("零億","億");
                     rstr=rstr.Replace("零萬","零");
                     rstr=rstr.Replace("零零","零");
                     rstr=rstr.Replace("零零","零");
                }
               }
               strlen=rstr.Length;
               if (strlen>=2)
               {
                    switch(rstr.Substring(strlen-2,2))
                    {
                         case "佰零":rstr=rstr.Substring(0,strlen-2)+"佰"; break;
                         case "仟零":rstr=rstr.Substring(0,strlen-2)+"仟"; break;
                         case "萬零":rstr=rstr.Substring(0,strlen-2)+"萬";break;
                         case "億零":rstr=rstr.Substring(0,strlen-2)+"億";break;
                    }
               }
               return rstr;
          }

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