读懂正则表达式就这么简单

<div class="post_item">
<div class="digg">
 <div class="diggit" onclick="DiggIt(3439076,120879,1)"> 
 <span class="diggnum" id="digg_count_3439076">4</span>
 </div>
 <div class="clear"></div> 
 <div id="digg_tip_3439076" class="digg_tip"></div>
</div> 
<div class="post_item_body">
 <h3><a class="titlelnk" href="http://www.cnblogs.com/swq6413/p/3439076.html" target="_blank">分享完整的项目工程目录结构</a></h3>   
 <p class="post_item_summary">
<a href="http://www.cnblogs.com/swq6413/" target="_blank"><img width="48" height="48" class="pfs" src="/UploadFiles/2021-04-02/20131116170946.png">

 通过构造一个Http请求来取到数据并对数据进行相应处理得到关键信息，在过滤Html标签取文章时正则的强大的威力就体现出来了，
正则的知识点也都基本用上了比如 "\s \w+ . * "还有捕获分组，零宽断言等等。喜欢的朋友可以试一试，然后自己看如何通过正则取相应数据的，代码中的正则都是很基本简单的，其意思与用法都在上文中详细写了。


class Program
 {
 static void Main(string[] args)
 {
  string content = HttpUtility.HttpGetHtml();
  HttpUtility.GetArticles(content);
 }
 }
 internal class HttpUtility
 {
 //默认获取第一页数据
 public static string HttpGetHtml()
 {
  HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://www.cnblogs.com/");
  request.Accept = "text/plain, */*; q=0.01";
  request.Method = "GET";
  request.Headers.Add("Accept-Language", "zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3");
  request.ContentLength = 0;
  request.Host = "www.cnblogs.com";
  request.UserAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.1 (KHTML, like Gecko) Maxthon/4.1.3.5000 Chrome/26.0.1410.43 Safari/537.1";
  HttpWebResponse response = (HttpWebResponse)request.GetResponse();
  Stream responStream = response.GetResponseStream();
  StreamReader reader = new StreamReader(responStream, Encoding.UTF8);
  string content = reader.ReadToEnd();
  return content;
 }
 public static List<Article> GetArticles(string htmlString)
 {
  List<Article> articleList = new List<Article>();
  Regex regex = null;
  Article article = null;
  regex = new Regex("<div class=\"post_item\">("clear\">" + @"</div>\s*</div>)",
    RegexOptions.Singleline);
  if (regex.IsMatch(htmlString))
  {
  MatchCollection aritcles = regex.Matches(htmlString);
  foreach (Match item in aritcles)
  {
   article = new Article();
   //取推荐
   regex =
   new Regex(
    "<div class=\"digg\">.*<span.*>(" + @"</span>" +
    ".*<div class=\"post_item_body\">", RegexOptions.Singleline);
   article.DiggNum = regex.Match(item.Value).Groups["digNum"].Value;
   //取文章标题 需要去除转义字符
   regex = new Regex("<h3>(", RegexOptions.Singleline);
   string a = regex.Match(item.Value).Groups["a"].Value;
   regex = new Regex("<a\\s.*href=\"(".*>(", RegexOptions.Singleline);
   article.AritcleUrl = regex.Match(a).Groups["href"].Value;
   article.AritcleTitle = regex.Match(a).Groups["summary"].Value;
   //取作者图片 
   regex = new Regex("<a.*>(", RegexOptions.Singleline);
   article.AuthorImg = regex.Match(item.Value).Groups["img"].Value;
   //取作者博客URL及链接的target属性
   regex = new Regex("<a\\s*"("\\s*"(">.*</a>",
     RegexOptions.Singleline);
   article.AuthorUrl = regex.Match(item.Value).Groups["href"].Value;
   string urlTarget = regex.Match(item.Value).Groups["target"].Value;
   //取文章简介
   //1 先取summary Div中所有内容
   regex = new Regex("<p class=\"post_item_summary\">(", RegexOptions.Singleline);
   string summary = regex.Match(item.Value).Groups["summary"].Value;
   //2 取简介
   regex = new Regex("(", RegexOptions.Singleline);
   article.AritcleInto = regex.Match(summary).Groups["indroduct"].Value;
   //取发布人与发布时间
   regex =
   new Regex(
    "<div class=\"post_item_foot\">\\s*<a.*"article_comment\">",
    RegexOptions.Singleline);
   article.Author = regex.Match(item.Value).Groups["publishName"].Value;
   article.PublishTime = regex.Match(item.Value).Groups["publishTime"].Value.Trim();
   //取评论数
   regex =
   new Regex(
    "<span class=\"article_comment\"><a.*>("article_view\">",
    RegexOptions.Singleline);
   article.CommentNum = regex.Match(item.Value).Groups["comment"].Value;
   //取阅读数
   regex = new Regex("<span\\s*class=\"article_view\"><a.*>(", RegexOptions.Singleline);
   article.ReadNum = regex.Match(item.Value).Groups["readNum"].Value;
   articleList.Add(article);
  }
  }
  return articleList;
 }
 public static string ClearSpecialTag(string htmlString)
 {
  string htmlStr = Regex.Replace(htmlString, "\n", "", RegexOptions.IgnoreCase);
  htmlStr = Regex.Replace(htmlStr, "\t", "", RegexOptions.IgnoreCase);
  htmlStr = Regex.Replace(htmlStr, "\r", "", RegexOptions.IgnoreCase);
  htmlStr = Regex.Replace(htmlStr, "\"", "'", RegexOptions.IgnoreCase);
  return htmlStr;
 }
 }
 public class Article
 {
 /// <summary>
 /// 文章标题
 /// </summary>
 public string AritcleTitle { get; set; }
 /// <summary>
 /// 文章链接
 /// </summary>
 public string AritcleUrl { get; set; }
 /// <summary>
 /// 文章简介
 /// </summary>
 public string AritcleInto { get; set; }
 /// <summary>
 /// 作者名
 /// </summary>
 public string Author { get; set; }
 /// <summary>
 /// 作者地址
 /// </summary>
 public string AuthorUrl { get; set; }
 /// <summary>
 /// 作者图片
 /// </summary>
 public string AuthorImg { get; set; }
 /// <summary>
 /// 发布时间
 /// </summary>
 public string PublishTime { get; set; }
 /// <summary>
 /// 推荐数
 /// </summary>
 public string DiggNum { get; set; }
 /// <summary>
 /// 评论数
 /// </summary>
 public string CommentNum { get; set; }
 /// <summary>
 /// 阅读数
 /// </summary>
 public string ReadNum { get; set; }
 }


 正则部分可能写得不很完美，但至少也匹配出来了，另外因为自己也是刚接触正则，也只能写出这种比较简单的正则。还望大家海涵~~
五    总结
　　正则其实并不难，了解每个符号的意思后，自己马上动手试一试多写几次自然就明白了，正则是出了名的坑多，随便少写了个点就匹配不到数据了，我也踩了很多坑，踩着踩着就踩出经验了。
本文也只是对正则做了很基本的介绍，还有很多正则的字符没有介绍，只是写了比较常用的一些。如有错误之处，还望在评论中指出，我会马上修改。
好了，关于正则表达式知识就给大家介绍这么多，希望对大家有所帮助，如果大家有任何疑问欢迎给我留言，小编会及时回复大家的，在此也非常感谢大家对网站的支持！