的基础上，根据自己的需求加以改进，获取标记中的所有内容信息

测试数据：

<div style="background-color:gray;" id="footer">
<a id="gotop" href="#" onclick="MGJS.goTop();return false;">Top</a>
<a id="powered" href="http://wordpress.org/">WordPress</a>
<div id="copyright">
Copyright &copy; 2009 简单生活 —— Kevin Yang的博客 </div>
<div id="themeinfo">
Theme by <a href="http://www.neoease.com/">mg12</a>.
Valid <a href="http://validator.w3.org/check?uri=referer">XHTML 1.1</a>
and <a href="http://jigsaw.w3.org/css-validator/">CSS 3</a>
</div>
<div/>
<p/>
</div>

修改过后的正则：

<(?<HtmlTag>[\w]+)[^>]*\s[iI][dD]=(?<Quote>["']?)footer(?(Quote)\k<Quote>)[^>]*?(/>|>(?<innerHtml>((?<Nested><\k<HtmlTag>[^>]*>)|</\k<HtmlTag>>(?<-Nested>)|[\s\S]*?)*)</\k<HtmlTag>>)

主要改正二处：

1，加了命名组innerHTML获取内部所有内容

2，最后部分>)|[.*?)*)</\k<HtmlTag>>)改成了[\s\S]以适应多行

C# 调用代码：

  // Regex match
            RegexOptions options = RegexOptions.None;
            Regex regex = new Regex(@"<(?<HtmlTag>[\w]+)[^>]*\s[iI][dD]=(?<Quote>[""']?)footer(?(Quote)\k<Quote>)[^>]*?(/>|>(?<innerHtml>((?<Nested><\k<HtmlTag>[^>]*>)|</\k<HtmlTag>>(?<-Nested>)|[\s\S]*?)*)</\k<HtmlTag>>)",options);
            string input = @"<div style=""background-color:gray;"" id=""footer"">
    <a id=""gotop"" href=""#"" onclick=""MGJS.goTop();return false;"">Top</a>
    <a id=""powered"" href=""http://wordpress.org/"">wordpress</a>
    <div id=""copyright"">
        Copyright &copy; 2009 简单生活 —— Kevin Yang的博客    </div>
    <div id=""themeinfo"">
        Theme by <a href=""http://www.neoease.com/"">mg12</a>.
 Valid <a href=""http://validator.w3.org/check?uri=referer"">XHTML 1.1</a>
        and <a href=""http://jigsaw.w3.org/css-validator/"">CSS 3</a>
    </div>
<div/>
<p/>
 </div> ";

            // Check for match
            bool isMatch = regex.IsMatch(input);
            if (isMatch)
            {
                // TODO: Do something with result
                MessageBox.Show(input,"IsMatch");
            }

            // Get match
            Match match = regex.Match(input);

            // Get matches
            MatchCollection matches = regex.Matches(input);
            for (int i = 0; i != matches.Count; ++i)
            {
                // TODO: Do something with result
                MessageBox.Show(matches[i].Value,"Match");
            }

            // Numbered groups
            for (int i = 0; i != match.Groups.Count; ++i)
            {
                Group group = match.Groups[i];

                // TODO: Do something with result
                MessageBox.Show(group.Value,"Group: " + i);
            }

            // Named groups
            string groupA = match.Groups["HtmlTag"].Value;
            string groupB = match.Groups["innerHtml"].Value;

            // TODO: Do something with result
            MessageBox.Show(groupA,"Group: HtmlTag");
            MessageBox.Show(groupB,"Group: innerHtml");