在Haystack中查找字符串并显示找到该字符串的特定段落

• 把文本串成一个字符串。
• text.split('\n')
• 在每个段落上迭代
• text.IndexOf("keyword")
• 然后执行一些逻辑来减少开头和结尾的字符数
• 插入粗体标记,例如字符串替换- text = text.Replace("keyword", "<b>keyword</b>")

public List<string> HighLightedParagraphs(string word, string text)
{
    int charBeforeAndAfter = 100;
    List<string> matchParagraphs = new List<string>();
    Regex wordMatch = new Regex(@"\b" + word + @"\b", RegexOptions.IgnoreCase);
    foreach (string paragraph in text.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries))
    {
        int startIdx = -1;
        int length = -1;
        foreach (Match match in wordMatch.Matches(paragraph))
        {
            int wordIdx = match.Index;
            if (wordIdx >= startIdx && wordIdx <= startIdx + length) continue;
            startIdx = wordIdx > charBeforeAndAfter ? wordIdx - charBeforeAndAfter : 0;
            length = wordIdx + match.Length + charBeforeAndAfter < paragraph.Length
                                ? match.Length + charBeforeAndAfter
                                : paragraph.Length - startIdx;
            string extract = wordMatch.Replace(paragraph.Substring(startIdx, length), "<b>" + match.Value + "</b>");
            matchParagraphs.Add("..." + extract + "...");
        }
    }
    return matchParagraphs;
}