c#中怎么用正则表达式抓取不固定的图片链接

 <img src="https://ununsplash.imgix.net/photo-1428604467652-115d9d71a7f1?fit=crop&amp;fm=jpg&amp;h=700&amp;q=75&amp;w=1050" class="img-responsive js-fluid-image js-packery-image">


<img src="https://ununsplash.imgix.net/photo-1429760575641-c599a08c3541?fit=crop&amp;fm=jpg&amp;h=700&amp;q=75&amp;w=1050" class="img-responsive js-fluid-image js-packery-image" >

类似这种标签是怎么抓取的，
在下小白，请大神详解，先谢谢各位啦~

         string s="<img src=\"https://ununsplash.imgix.net/photo-1428604467652-115d9d71a7f1?fit=crop&amp;fm=jpg&amp;h=700&amp;q=75&amp;w=1050\" class=\"img-responsive js-fluid-image js-packery-image\">"
            +"<img src=\"https://ununsplash.imgix.net/photo-1429760575641-c599a08c3541?fit=crop&amp;fm=jpg&amp;h=700&amp;q=75&amp;w=1050\" class=\"img-responsive js-fluid-image js-packery-image\" >";

        MatchCollection mc = Regex.Matches(s, "<img\\s+src=\"([^\"]+)\"", RegexOptions.IgnoreCase);
        foreach (Match m in mc) Response.Write(m.Groups[1].Value+"<br>");

 https\:\/\/ununsplash\.imgix\.net\/photo\-.+?w\=\d+

 (?<=src=")[^"]*(?=")

参考下：http://blog.csdn.net/lhfly/article/details/7684319