将数字按照3位一组添加逗号的正则替换

这段正则使用了前瞻的方法，匹配的数字后面必须有3的n倍个数字，保证3个为1组，并将匹配出来的数字后面添加逗号。（正负数通杀）

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 using System.Text.RegularExpressions;
 6 using System.Threading.Tasks;
 7 
 8 namespace MyRegexTest
 9 {
10     class Program
11     {
12         static void Main(string[] args)
13         {
14             List<string> list = new List<string>() { "1", "12", "123", "1234", "12345", "123456", "1234567", 
15                 "12345678", "123456789", "1234567890"};
16             foreach (var s in list)
17             {
18                 Console.WriteLine(Regex.Replace(s, @"(d+?)(?=(?:d{3})+$)", "$1,"));
19             }
20 
21             Console.ReadKey();
22         }
23     }
24 }

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refer to:http://www.cnblogs.com/fysn/archive/2012/02/24/2367024.html