这个正则表达式如何写？

Question

gfdgf<img alt="" src="http://localhost/saasent/upload/attachment/epid_1/bbs/20100416/em_1/20100416115401.jpg" /><br />f<br />ds<br />fsd<br />fds<br />fsd<br />fds<img alt="" src="http://localhost/saasent/upload/attachment/epid_1/bbs/20100416/em_1/20100416115408.jpg" />我想要找到上面文本的第一个标签<img>里面的src值，如何做？
<img alt="" src="http://localhost/saasent/upload/attachment/epid_1/bbs/20100416/em_1/20100416115401.jpg" />

Answer 1

(?<=<img\s+((?!src).)*src=")[^"]+

Answer 2

try...string test = "gfdgf<img alt=\"\" src=\"http://localhost/saasent/upload/attachment/epid_1/bbs/20100416/em_1/20100416115401.jpg\" /><br />f<br />ds<br />fsd<br />fds<br />fsd<br />fds<img alt=\"\" src=\"http://localhost/saasent/upload/attachment/epid_1/bbs/20100416/em_1/20100416115408.jpg\" />";
Regex reg = new Regex(@"(?i)<img\b[^>]*?src\s*=\s*(['""]?)([^'""\s>]+)\1[^>]*>");
Match m = reg.Match(test);
if (m.Success)
{
    Response.Write(m.Groups[2].Value);
}

Answer 3

<img(.*?) src=["|'](.*?)["|'](.*?)/> 匹配img标签，接下来根据需要处理