c# - Regex 和 span 类如何在此代码中工作？

Question

我继承了一个网站的代码，这个特殊的函数用于在给定部件号时从网站获取描述。我以前从未使用过正则表达式，所以这个集合有点超出我的范围，并且希望得到一些帮助来弄清楚为什么它不能正常工作。

本质上，此功能的理想操作是，当站点的用户在适当的字段中输入零件编号并按下按钮时，将从单独的站点获得的标准零件描述输出给用户.我检查了正则表达式试图匹配的第三方网站上的元素，它被编码为

<span id="ctl00_BodyContentPlaceHolder_lblDescription">Random Description</span>

public static string GetPartHpDescription(string url)
    {

        // Create a request to the url
        HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;

        // If the request wasn't an HTTP request (like a file), ignore it
        if (request == null) return null;

        // Use the user's credentials
        request.UseDefaultCredentials = true;

        // Obtain a response from the server, if there was an error, return nothing
        HttpWebResponse response = null;
        try { response = request.GetResponse() as HttpWebResponse; }
        catch (WebException) { return null; }

        // Regular expression for an HTML title
        //  string regex = @"(?<=<body.*>)([Description : HP]*)(?=</body>)";
        string regex = "<span [^>]*id=(\"|')ctl00_BodyContentPlaceHolder_lblDescription(\"|')>(.*?)</span>";
        string regex1 = "<span [^>]*id=(\"|')ctl00_BodyContentPlaceHolder_gvGeneral_ctl02_lblpartdesc1(\"|')>(.*?)</span>";
        // Regex re = new Regex(@"<span\s+id=""ctl00_BodyContentPlaceHolder_lblDescription");
        // string regex =  @"<span\s+id=""ctl00_BodyContentPlaceHolder_lblDescription"
        // If the correct HTML header exists for HTML text, continue
        if (new List<string>(response.Headers.AllKeys).Contains("Content-Type"))
            if (response.Headers["Content-Type"].StartsWith("text/html"))
            {
                // Download the page
                WebClient web = new WebClient();
                web.UseDefaultCredentials = true;
                string page = web.DownloadString(url);
                // string title = Regex.Match(page, @"<span\s+id=""ctl00_BodyContentPlaceHolder_lblDescription"">.*?</span>", RegexOptions.IgnoreCase).Groups["Title"].Value;
                // Extract the title
                Regex ex = new Regex(regex, RegexOptions.IgnoreCase);
                String data = ex.Match(page).Value.Trim();
                if (data == "")
                {
                    Regex ex1 = new Regex(regex1, RegexOptions.IgnoreCase);
                    data = ex1.Match(page).Value.Trim();
                }
                return data;
                //   return title;
            }

        // Not a valid HTML page
        return null;
    }

当前发生的情况是，如果零件号当前不在系统数据库(sql 后端)中，则该函数无法正确获取零件描述。

Answer 1

我的猜测是我们有一些 ID 希望提取它们的 textContnet，如果我们必须使用正则表达式来这样做，我们将从一个简单的表达式开始，然后如果有必要，我们将添加更多约束，

<span id=["'](ctl00_.+|other_ids)["']>(.+?)<\/span>

Demo

using System;
using System.Text.RegularExpressions;

public class Example
{
    public static void Main()
    {
        string pattern = @"<span id=[""'](ctl00_.+|other_ids)[""']>(.+?)<\/span>";
        string input = @"<span id=""ctl00_BodyContentPlaceHolder_lblDescription"">Random Description</span>
<span id='ctl00_BodyContentPlaceHolder_lblDescription'>Random Description</span>
";
        RegexOptions options = RegexOptions.Multiline;

        foreach (Match m in Regex.Matches(input, pattern, options))
        {
            Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
        }
    }
}

正则表达式电路

jex.im可视化正则表达式: