如何使用 RegEx 从 HTML 中提取值？

Question

给定以下 HTML：

<p><span class="xn-location">OAK RIDGE, N.J.</span>, <span class="xn-chron">March 16, 2011</span> /PRNewswire/ -- Lakeland Bancorp, Inc. (Nasdaq:   <a href='http://studio-5.financialcontent.com/prnews?Page=Quote&Ticker=LBAI' target='_blank' title='LBAI'> LBAI</a>), the holding company for Lakeland Bank, today announced that it redeemed <span class="xn-money">$20 million</span> of the Company's outstanding <span class="xn-money">$39 million</span> in Fixed Rate Cumulative Perpetual Preferred Stock, Series A that was issued to the U.S. Department of the Treasury under the Capital Purchase Program on <span class="xn-chron">February 6, 2009</span>, thereby reducing Treasury's investment in the Preferred Stock to <span class="xn-money">$19 million</span>. The Company paid approximately <span class="xn-money">$20.1 million</span> to the Treasury to repurchase the Preferred Stock, which included payment for accrued and unpaid dividends for the shares. &#160;This second repayment, or redemption, of Preferred Stock will result in annualized savings of <span class="xn-money">$1.2 million</span> due to the elimination of the associated preferred dividends and related discount accretion. &#160;A one-time, non-cash charge of <span class="xn-money">$745 thousand</span> will be incurred in the first quarter of 2011 due to the acceleration of the Preferred Stock discount accretion. &#160;The warrant previously issued to the Treasury to purchase 997,049 shares of common stock at an exercise price of <span class="xn-money">$8.88</span>, adjusted for stock dividends and subject to further anti-dilution adjustments, will remain outstanding.</p>

我想获取 元素内的值。我还想获取 元素上的 class 属性的值。

理想情况下，我可以通过函数运行一些 HTML 并返回提取实体的字典（基于上面定义的 解析）。

上面的代码是来自一个较大的 HTML 源文件的片段，它无法与 XML 解析器进行匹配。所以我正在寻找一个可能的正则表达式来帮助提取感兴趣的信息。

Answer 1

使用此工具（免费）：
http://www.radsoftware.com.au/regexdesigner/

使用此正则表达式：

"<span[^>]*>(.*?)</span>"

第 1 组中的值（对于每场比赛）将是您需要的文本。

在 C# 中，它看起来像：

            Regex regex = new Regex("<span[^>]*>(.*?)</span>");
            string toMatch = "<span class=\"ajjsjs\">Some text</span>";
            if (regex.IsMatch(toMatch))
            {
                MatchCollection collection = regex.Matches(toMatch);
                foreach (Match m in collection)
                {
                    string val = m.Groups[1].Value;
                    //Do something with the value
                }
            }

---

修正回答评论：

            Regex regex = new Regex("<span class=\"(.*?)\">(.*?)</span>");
            string toMatch = "<span class=\"ajjsjs\">Some text</span>";
            if (regex.IsMatch(toMatch))
            {
                MatchCollection collection = regex.Matches(toMatch);
                foreach (Match m in collection)
                {
                    string class = m.Groups[1].Value;
                    string val = m.Groups[2].Value;
                    //Do something with the class and value
                }
            }

Answer 2

假设您没有嵌套 span 标签，则以下内容应该有效：

/]+class=\"(.*?)\"[^ >]*)?>(.*?)<\/span>/

我只对它做了一些基本测试，但它会匹配 span 标签的类（如果存在）直到标签关闭为止。

Answer 3

我强烈建议您使用真正的 HTML 或 XML 解析器来代替。 您无法使用正则表达式可靠地解析 HTML 或 XML ——你能做的最多就是接近，你越接近，你的正则表达式就会越复杂和耗时。如果您有一个大型 HTML 文件需要解析，则很可能会破坏任何简单的正则表达式模式。

像 ]*>(.*?) 这样的正则表达式将适用于您的示例，但是有很多 XML 有效的代码很难甚至是不可能的使用正则表达式进行解析（例如， foo bar 将打破上述模式）。如果您想要一些可以在其他 HTML 示例上运行的东西，那么正则表达式不是您的最佳选择。

由于您的 HTML 代码不是 XML 有效的，因此请考虑使用 HTML Agility Pack ，我听说非常好。