正则 截取固定开头结尾字符串中间的字符串,该怎么解决

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

        string str = "class=&amp;quot;g&amp;quot;&amp;gt;topic.csdn.net/u/20091018/11/ef331a56-93f ... 2011-3-28 &amp;lt;/span&amp;gt; - &amp;lt;a";
        Regex reg = new Regex(@"(?s)(?<……