求一正则解决方案_ASP.NET

求一正则
[<a href="">经验窍门</a>]<a href="thjy.co" onClick="atarget(this)" class="xst">sfasdf</a>
<img src="static/image/common/hot_3.gif" alt="heatlevel" title="3 级热门" align="absmiddle">
[<a href="">经验窍门</a>]<a href="bbs.thjy.co" onClick="atarget(this)" class="xst">sfasdf</a>
<img src="static/image/common/hot_3.gif" alt="heatlevel" title="3 级热门" align="absmiddle">
[<a href="">经验窍门</a>]<a href="test.thjy.co" onClick="atarget(this)" class="xst">sfasdf</a>
<img src="static/image/common/hot_3.gif" alt="heatlevel" title="3 级热门" align="absmiddle">

把带有onClick="atarget(this)" 的a标签全部取出来结果如下:
thjy.co
bbs.thjy.co
test.thjy.co

那位高手解答下谢谢

------解决方案--------------------------------------------------------

C# code

            string str = @"<em>[<a href="""">经验窍门</a>]</em><a href=""thjy.co"" onClick=""atarget(this)"" class=""xst"">sfasdf</a><img src=""static/image/common/hot_3.gif"" alt=""heatlevel"" title=""3 级热门"" align=""absmiddle""> <em>[<a href="""">经验窍门</a>]</em><a href=""bbs.thjy.co"" onClick=""atarget(this)"" class=""xst"">sfasdf</a><img src=""static/image/common/hot_3.gif"" alt=""heatlevel"" title=""3 级热门"" align=""absmiddle""> <em>[<a href="""">经验窍门</a>]</em><a href=""test.thjy.co"" onClick=""atarget(this)"" class=""xst"">sfasdf</a><img src=""static/image/common/hot_3.gif"" alt=""heatlevel"" title=""3 级热门"" align=""absmiddle"">";            Regex reg = new Regex(@"(?i)<a\s*href=""(?<url>[^""]+)""\s+onclick=""atarget\(this\)""");            MatchCollection mc = reg.Matches(str);            foreach (Match m in mc)            {                Console.WriteLine(m.Groups["url"].Value);            }
------解决方案--------------------------------------------------------
Regex reg = new Regex(@"(?i)<a[^>]*?href=(['""\s]?)(?<url>[^\s'""]+)\1\s+onclick=(['""\s]?)atarget\(this\)\2");