string str = @"<a href=""xx.xx"">xx</a><a href=""xx.xx"">xx</a>
<div>不确定字符串<a href=""1.xx"">xx</a>不确定字符串<a href=""2.xx"">xx</a>不确定字符串</div>
<p><a href=""xx.xx"">xx</a><a href=""xx.xx"">xx</a></p>";
            Regex reg = new Regex(@"(?is)<div[^>]*?>(?:.*?<a[^>]*?href=(['""\s]?)([^'""\s]+)\1[^>]*?>.*?</a>)*.*?</div>");
            foreach (Capture c in reg.Match(str).Groups[2].Captures)
                Console.WriteLine(c.Value);



            Regex reg1 = new Regex(@"(?is)(?<=<div[^>]*?>(?:(?!</?div).)*)<a[^>]*?href=(['""\s]?)([^'""\s]+)\1[^>]*?>");
            foreach (Match m in reg1.Matches(str))
                Console.WriteLine(m.Groups[2].Value);

------解决方案--------------------


如果有个test的ID，这样应该是可以的
C# code


Regex re = new Regex("<div[^>]*id=\"test\">[^<]+<a\\s*href=\"([^\"]+)\">[^<]+</a>[^<]+<a\\s*href=\"([^\"]+)\">[^<]+</a>[^<]+</div>", RegexOptions.None);