原文发布时间为：2009-11-21 —— 来源于本人的百度文章 [由搬家工具导入]
请先学习：http://hi.baidu.com/handboy/blog/item/bfef61000a67ea16738b6565.html
string x = "Live for nothing,die for something";
Regex r = new Regex(@"^Live for no(?<g1>[a-z]{5}),die for some\1$");
if (r.IsMatch(x))
{
Console.WriteLine("group1 value:" + r.Match(x).Groups["g1"].Value);//输出：thing
}
//可根据组名进行索引。使用以下格式为标识一个组的名称(?<groupname>…)。
string x = "Live for nothing nothing";
Regex r = new Regex(@"([a-z]+) \1");
if (r.IsMatch(x))
{
x = r.Replace(x, "$1");
Console.WriteLine("var x:" + x);//输出：Live for nothing
}
//删除原字符串中重复出现的“nothing”。在表达式之外，使用“$1”来引用第一个组，下面则是通过
组名来引用：
string x = "Live for nothing nothing";
Regex r = new Regex(@"(?<g1>[a-z]+) \1");
if (r.IsMatch(x))
{
x = r.Replace(x, "${g1}");
Console.WriteLine("var x:" + x);//输出：Live for nothing
}
string x = "Live for nothing";
Regex r = new Regex(@"^Live for no(?:[a-z]{5})$");
if (r.IsMatch(x))
{
Console.WriteLine("group1 value:" + r.Match(x).Groups[1].Value);//输出：(空)
}
//在组前加上“?:”表示这是个“非捕获组”，即引擎将不保存该组的内容。
========
最近闲来无事，重温了一下正则表达式，然后做了这个 图片抓取器。
原则就是 根据分析 新浪博文的共同特征，把图片抓取到本地下来，自动下载下来。 这个原理就是用 正则表达式去匹配，如果有一天新浪博文网页格式变化了，可能这个就用不了了，但是可以进行修改去满足。这只是一个范例，O(∩_∩)O哈！
winform下载预览：http://www.xmaspx.com/Services/FileAttachment.ashx?AttachmentID=51
首先：
在根目录下，建一个名为 DownLoadImages 的文件夹
前台：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="SinaImage.aspx.cs" Inherits="SinaImage" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server" Width="495px">http://blog.sina.com.cn/s/articlelist_1270540911_0_1.html</asp:TextBox>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" OnClientClick="javascript:alert('开始下载，可能要等几分钟，请勿关闭')" /><br />
<asp:TextBox ID="TextBox2" runat="server" Height="296px" TextMode="MultiLine" Width="498px"></asp:TextBox></div>
</form>
</body>
</html>
后台：
using System;
using System.Web;
using System.Web.UI.WebControls;
using System.Net;
using System.IO;
using System.Text;
using System.Collections;
using System.Text.RegularExpressions;
public partial class SinaImage : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
int num = 0;
TextBox2.Text = "";
string p = @"http://blog.sina.com.cn/s/blog_([\w])*.html";
string p2 = @"http://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
ArrayList arrUrl = GetUrl(this.TextBox1.Text, p);
for (int i = 0; i < arrUrl.Count; i++)
{
string imgPage = arrUrl[i].ToString();
ArrayList arrImgUrl = GetUrl(imgPage, p2);
for (int j = 0; j < arrImgUrl.Count; j++)
{
string imgUrl = arrImgUrl[j].ToString();
if (!imgUrl.Contains("simg") && !imgUrl.Contains("sinaimg") && !imgUrl.Contains(".js"))
{
if (imgUrl.Contains("photo") || imgUrl.Contains("image") || imgUrl.Contains("img"))
{
TextBox2.Text += imgUrl + "\n";
try
{
DownLoadImage(imgUrl, j.ToString());
num++;
}
catch
{
}
}
}
}
}
ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('下载了" + num.ToString() + "张，请打开文件夹DownLoadImages，以缩略图形式进行筛选')", true);
}
protected void DownLoadImage(string fromUrl, string fileName)
{
string savePath = Server.MapPath("DownLoadImages/") + DateTime.Now.ToString("yyyyMMddhhmmss") + fileName + ".jpg";
WebClient myWebClient = new WebClient();
myWebClient.DownloadFile(fromUrl, savePath);
}
protected ArrayList GetUrl(string web_url, string p)
{
string all_code = string.Empty;
ArrayList arrUrl = new ArrayList();
HttpWebRequest all_codeRequest = (HttpWebRequest)WebRequest.Create(web_url);
WebResponse all_codeResponse = all_codeRequest.GetResponse();
StreamReader the_Reader = new StreamReader(all_codeResponse.GetResponseStream(), Encoding.GetEncoding("GB2312"));
all_code = the_Reader.ReadToEnd();
the_Reader.Close();
ArrayList my_list = new ArrayList();
Regex re = new Regex(p, RegexOptions.IgnoreCase);
MatchCollection mc = re.Matches(all_code);
for (int i = 0; i <= mc.Count - 1; i++)
{
bool _foo = false;
string name = mc[i].ToString();
foreach (string list in my_list)
{
if (name == list)
{
_foo = true;
break;
}
}//过滤
if (!_foo)
{
arrUrl.Add(name);
}
}
return arrUrl;
}
}