//导入:using System.Text.RegularExpressions;
//测试成功
string str = "<a href=/"/z/q160049681.htm/" target=/"_blank/">";
Regex re = new Regex(@"<a[^>]+href=/s*(?:'(?<href>[^']+)'|""(?<href>[^""]+)""|(?<href>[^>/s]+))/s*[^>]*>", RegexOptions.IgnoreCase | RegexOptions.Singleline);
MatchCollection mc = re.Matches(str);
Console.WriteLine(mc.Count);
foreach (Match m in mc)
Response.Write(m.Groups["href"].Value);
//输出结果为:/z/q160049681.htm