比如：class="g">topic.csdn.net/u/20091018/11/ef331a56-93f ... 2011-3-28 </span> - <a其中以class="g">开头 ；</span> - <a结尾如何获取中间的字符串：topic.csdn.net/u/20091018/11/ef331a56-93f ... 2011-3-28

 

string str = "class="g">topic.csdn.net/u/20091018/11/ef331a56-93f ... 2011-3-28 </span> - <a";        Regex reg = new Regex(@"(?s)(?<=class="g">).*(?=</span> - <a)");        foreach (Match m in reg.Matches(str))        {            Response.Write(m.Value + "
");        }//topic.csdn.net/u/20091018/11/ef331a56-93f ... 2011-3-28

应多加个？，如下：

@"(?s)(?<=class=&quot;g&quot;&gt;).*?(?=&lt;/span&gt; - &lt;a)"

原因是str一般是网页的源码，里面相同的内容比较多，避免匹配多余的内容！