Demo源码如下：

Demo下载地址：http://download.csdn.net/detail/zxcvbnm32123/5830571

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;

namespace _12提取html中的所有的Email地址
{
    class Program
    {
        static void Main(string[] args)
        {
            string html = File.ReadAllText("1.htm");
            //提取Email
            //通过（）提取组,正则表达式如下
            string regEmail = @"([a-zA-Z0-9_\-\.]+)@([a-zA-Z0-9]+)(\.[a-zA-Z0-9])+";
            MatchCollection mc = Regex.Matches(html,regEmail);
            //请统计出常用邮件服务提供商的用户使用。
            //163
            //126
            //sohu
            //gmail
            //qq
            //sina
            //yahoo
            //hotmail
            int count_163 = 0;
            int count_126 = 0;
            int count_gmail = 0;
            int count_qq = 0;
            int count_sohu = 0;
            int count_sina = 0;
            int count_yahoo = 0;
            int count_hotmail = 0;
            foreach (Match match in mc)
            {
                #region MyRegion
                //match.Groups[0].Value中存储的值遇match.Value中存储的值是一样的
                //表示提取到的Email的完整字符串
                //match.Value
                Console.WriteLine(match.Value);
                switch (match.Groups[2].Value)
                {
                    //default:
                }
                Console.WriteLine(match.Groups[0].Value);//0：完整邮箱名
                Console.WriteLine(match.Groups[1].Value);//:1：用户名
                Console.WriteLine(match.Groups[2].Value);//:2：域名
                Console.WriteLine(match.Groups[3].Value);//:3：组织名
                #endregion

                Console.WriteLine(match.Value);//输出所有邮箱地址
                //通过match.Groups[]来获取提取组。注意：第0组存储的是完整匹配字符串，要获取组因该从索引1开始。
                switch (match.Groups[2].Value.ToLower())
                {
                    case "163":
                        count_163++;
                        break;
                    case "126":
                        count_126++;
                        break;
                    case "gmail":
                        count_gmail++;
                        break;
                    case "qq":
                        count_qq++;
                        break;
                    case "sohu":
                        count_sohu++;
                        break;
                    case "sina":
                        count_sina++;
                        break;
                    case "yahoo":
                        count_yahoo++;
                        break;
                    case "hotmail":
                        count_hotmail++;
                        break;
                }
            }
            Console.WriteLine("=============统计信息============");
            Console.WriteLine("邮箱总数：{0}",mc.Count);
            Console.WriteLine("网易163邮箱用户数：{0}",count_163);
            Console.WriteLine("网易126邮箱用户数：{0}",count_126);
            Console.WriteLine("gmail邮箱用户数：{0}",count_gmail);
            Console.WriteLine("QQ邮箱用户数：{0}",count_qq);
            Console.WriteLine("sohu邮箱用户数：{0}",count_sohu);
            Console.WriteLine("sina邮箱用户数：{0}",count_sina);
            Console.WriteLine("yahoo邮箱用户数：{0}",count_yahoo);
            Console.WriteLine("hotmail邮箱用户数：{0}",count_hotmail);
            Console.ReadKey();
        }
    }
}

“1.htm”截图如下：

通过调试控制，查看获取的全部网页字符串，截图如下：

输出结果如下：

Demo下载地址：http://download.csdn.net/detail/zxcvbnm32123/5830571