计数正则表达式替换 (C#) [英] Count regex replaces (C#)

问题描述

有没有办法计算 Regex.Replace 调用的替换次数?

Is there a way to count the number of replacements a Regex.Replace call makes?

例如for Regex.Replace("aaa", "a", "b"); 我想得到数字 3(结果是 "bbb");for Regex.Replace("aaa", "(?<test>aa?)", "${test}b"); 我想得到数字 2(结果是 "aabab").

E.g. for Regex.Replace("aaa", "a", "b"); I want to get the number 3 out (result is "bbb"); for Regex.Replace("aaa", "(?<test>aa?)", "${test}b"); I want to get the number 2 out (result is "aabab").

我能想到的方法:

1. 使用 MatchEvaluator 增加捕获的变量，手动进行替换
2. 获取一个 MatchCollection 并对其进行迭代，手动进行替换并保持计数
3. 首先搜索并获取一个 MatchCollection，从中获取计数，然后进行单独的替换

方法1和2需要手动解析$替换，方法3需要正则表达式匹配字符串两次.有没有更好的办法.

Methods 1 and 2 require manual parsing of $ replacements, method 3 requires regex matching the string twice. Is there a better way.

推荐答案

感谢 Chevex 和 Guffa.我开始寻找一种更好的方法来获得结果，并发现 Match 类中有一个 Result 方法可以进行替换.那是拼图缺失的那一块.下面的示例代码:

Thanks to both Chevex and Guffa. I started looking for a better way to get the results and found that there is a Result method on the Match class that does the substitution. That's the missing piece of the jigsaw. Example code below:

using System.Text.RegularExpressions;

namespace regexrep
{
    class Program
    {
        static int Main(string[] args)
        {
            string fileText = System.IO.File.ReadAllText(args[0]);
            int matchCount = 0;
            string newText = Regex.Replace(fileText, args[1],
                (match) =>
                {
                    matchCount++;
                    return match.Result(args[2]);
                });
            System.IO.File.WriteAllText(args[0], newText);
            return matchCount;
        }
    }
}

对于包含 aaa 的文件 test.txt，命令行 regexrep test.txt "(?<test>aa?)" ${test}b 会将 %errorlevel% 设置为 2 并且将文本更改为 aabab.

With a file test.txt containing aaa, the command line regexrep test.txt "(?<test>aa?)" ${test}b will set %errorlevel% to 2 and change the text to aabab.

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