我如何执行 csharp(或 perl)替换字符串更改循环中每个发生次数的变量(正则表达式)

我做了一个代码片段：http://rextester.com/RLPS43509

我认为下面的代码是最简单的方法：

using System;
using System.Text.RegularExpressions;
using System.Text;
namespace Rextester
{
    public class Program
    {
        public static string replaceAsWithWhatever(string inputText)
        {
            StringBuilder sb = new StringBuilder();
            Regex rx = new Regex("as");
            int prior = 0;
            foreach (Match match in rx.Matches(inputText))
            {
                int i = match.Index;
                // copy the text not matched in between
                sb.Append(inputText.Substring(prior, i - prior));
                // [optional] prepend some text before match 
                sb.Append(" [before replacement] ");
                // replace match with something, possibly permutation of match
                sb.Append(" [replacement of " + match.ToString() + "] ");
                // append text after match
                sb.Append(" [after replacement] ");
                prior = i + match.Length;
            }
            // copy remaining string after all matches to stringbuilder
            sb.Append(inputText.Substring(prior, inputText.Length - prior));
            return sb.ToString();
        }
        public static void Main(string[] args)
        {
            // test cases
            Console.WriteLine(replaceAsWithWhatever("text before as between as whatever"));
            Console.WriteLine(replaceAsWithWhatever("sentence without matches"));
            Console.WriteLine(replaceAsWithWhatever("as"));
            Console.WriteLine(replaceAsWithWhatever("as ass ;)"));
        }
    }
}

在我之前的回答中，我假设您希望能够在循环比赛时更改替换。但是，重读后，我想我明白了所问的内容。

我的解释：就像在 C 预处理器中一样#define您希望再次展开并匹配。

示例将字符串 "wordrd" 中的 /word/ 替换为 "echo wo"：

"wordrd" -> "echo word" -> "echo echo rd"

这里有一个严重的问题，如果替换也包含匹配项，您将看到一个无限的单词。

示例：将/ass/替换为"assassin"

"ass" -> "assassin" -> "assassinassin" -> etc.

为了避免无限循环/单词，此解决方案仅检查替换中最后一个匹配项的索引，并使用前一个匹配项 + 此偏移量作为最小索引。基本上：

示例：将字符串"assass"中的/ass/替换为"assassin"

"assass" -> "assassinass" -> "assassinassassin"

示例 将/as/替换为"ba"

"asss" -> "bass" -> "bbas" -> "bbba"

此处的代码：http://rextester.com/PSTV39802 及以下

using System;
using System.Text.RegularExpressions;
using System.Text;
/* Basically a context-free replacement, minus the infinite words */
namespace Rextester
{
    public class Program
    {
        public static string replace(string inputText, Regex find, string replacement)
        {
            // to avoid a situation like the following: replace ass with assassin in string ass
            // "ass" -> "assassin" -> "assassinassin" -> etc.
            // it is only allowed to match after the last match in the replacement
            // aka. if we were to replace "ass" with "assassin a" in string "assss" we'd get           
            // "ass" -> "assassin ass" -> "assassin aassassin a"
            int countToSkipInReplacement = 0;
            int minimumIndex = 0;
            Match m;
            // first check if the replacement contains matches as well
            m = find.Match(replacement);
            if (m.Success)
            {
                while (m.Success)
                {
                    countToSkipInReplacement = m.Index + 1;
                    m = m.NextMatch();
                } 
            }
            while(true)
            {
                // uncomment to see all forms in between
                //Console.WriteLine(inputText);
                // find a match
                m = find.Match(inputText);
                // skip until the minimum index is found
                while (m.Success && m.Index < minimumIndex)
                    m = m.NextMatch();
                // if it has no further matches, return current string
                if (!m.Success)
                    return inputText;
                // glue a new inputText together with the contents before, the replacements and whatever comes after
                inputText = inputText.Substring(0, m.Index) + 
                            replacement + 
                            inputText.Substring(m.Index + m.Length, inputText.Length - (m.Index + m.Length));
                // make sure it doesn't go back and replace the text it just inserted again.
                minimumIndex = m.Index + countToSkipInReplacement;
            }
        }
        public static void Main(string[] args)
        {
            Regex rx = new Regex("as");
            Console.WriteLine(replace("text before ass between as whatever", rx, "a"));
            Console.WriteLine(replace("sentence without matches", rx, "a"));
            Console.WriteLine(replace("as", rx, "a"));
            Console.WriteLine(replace("as", rx, "as"));
            Console.WriteLine(replace("assss", rx, "ba"));
        }
    }
}