如何在c#中匹配模式并提取出其中的一部分?

本文关键字：提取 一部分 模式 | 更新日期: 2023-09-27 18:06:46

我有以下文本在一个字符串中，总是以"?"结尾。

"Which of the following can be abc def ghi?"
"Which of the following can be hello?"

谁能告诉我如何检查这个文本是否包含:

"Which of the following <any string of text here>?"

如果它包含了这个那么我怎么能得到文本"abc def "answers"hello"

如何在c#中匹配模式并提取出其中的一部分?

const string constantValue = "Which of the following can be ";
var theString = "Which of the following can be abc def ghi?";
var index = theString.IndexOf(constantValue);
string result = "";
if (index > -1)
    result = theString.Substring(constantValue.Length, 
                            theString.Length - constantValue.Length - index - 1);
编辑:

这个正则表达式应该匹配来自其他问题的所有输入:

var text = "1 - Which of the following is a aa mmm zz?'n" +
"2 - Which of the following is true?'n" +
"3 - Which of the following can be aa mmm zz?'n" +
"4 - Which of the following are correct?'n" +
"5 - What will be the result when aa mmm zz?'n" +
"6 - What will result when aa mmm zz?'n" +
"7 - Which are aa mmm zz?'n" +
"8 - What can be said about aa mmm zz?'n";
var regex = @"What (can be said about |will (be the )?result when )(?<result>.*?)'?|Which (of the following )?(can be|are|is|is a) (?<result>.*?)[?:]";
var matches = Regex.Matches(text, regex);
foreach (Match match in matches)
{
    Console.WriteLine("result: " + match.Groups["result"]);
}

您可以使用String.StartsWith()来检查子字符串是否存在。
您可以使用Split()根据指定的子字符串拆分字符串。

你也可以使用正则表达式，如果你理解它们(我不懂…)

如果您只想匹配整个输入字符串，并确保输入字符串以问题的开头开始，则使用此:

  static string ExtractQuestionObject(string question)
  {
     const string pattern = "Which of the following ";
     if (question.StartsWith(pattern, StringComparison.CurrentCultureIgnoreCase)
         && question.EndsWith("?"))
        return question.Substring(pattern.Length, question.Length - pattern.Length - 1);
     else
        return null;
  }

如果你想在输入的任何地方找到问题，使用:

  static string FindQuestionObject(string text)
  {
     const string pattern = "Which of the following ";
     int questionStart = text.IndexOf(pattern);
     if (questionStart >= 0)
     {
        int questionMark = text.IndexOf('?', questionStart);
        if (questionMark > questionStart)
           return text.Substring(questionStart + pattern.Length,
                  questionMark - questionStart - pattern.Length);
     }
     return null;
  }

如果您想使用正则表达式在一次调用中匹配所有字符串，请使用:

  static string[] FindQuestionObjects(string text)
  {
     System.Text.RegularExpressions.Regex re = new System.Text.RegularExpressions.Regex(
        @"Which of the following ([^'?]+)'?",
        System.Text.RegularExpressions.RegexOptions.IgnoreCase);
     System.Text.RegularExpressions.MatchCollection mc = re.Matches(text);
     string[] result = new string[mc.Count];
     for(int i = 0; i < result.Length; i++)
        result[i] = mc[i].Groups[1].Value;
     return result;
  }

if (str.Length > "Which of the following".Length)
{
    Console.WriteLine(str.Replace("Which of the following", "").Replace("can be" , "").Trim());
}
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