正则表达式替换的C＃美元问题 [英] C# dollar problem with regex-replace

问题描述

我想在两个命名的捕获组之间的特定位置插入美元符号。问题是这意味着替换字符串中紧随两个美元符号会导致问题。

I want to insert a dollar sign at a specific position between two named capturing groups. The problem is that this means two immediately following dollar-signs in the replacement-string which results in problems.

我如何直接使用替换方法？我只是找到了一种解决方法，方法是添加一些临时垃圾，然后立即将其再次删除。

请参阅该问题的代码：

      // We want to add a dollar sign before a number and use named groups for capturing;
      // varying parts of the strings are in brackets []
      // [somebody] has [some-dollar-amount] in his [something]

      string joeHas = "Joe has 500 in his wallet.";
      string jackHas = "Jack has 500 in his pocket.";
      string jimHas = "Jim has 740 in his bag.";
      string jasonHas = "Jason has 900 in his car.";

      Regex dollarInsertion = new Regex(@"(?<start>^.*? has )(?<end>\d+ in his .*?$)", RegexOptions.Multiline);

      Console.WriteLine(joeHas);
      Console.WriteLine(jackHas);
      Console.WriteLine(jimHas); 
      Console.WriteLine(jasonHas);
      Console.WriteLine("--------------------------");

      joeHas = dollarInsertion.Replace(joeHas, @"${start}$${end}");
      jackHas = dollarInsertion.Replace(jackHas, @"${start}$-${end}");          
      jimHas = dollarInsertion.Replace(jimHas, @"${start}\$${end}");
      jasonHas = dollarInsertion.Replace(jasonHas, @"${start}$kkkkkk----kkkk${end}").Replace("kkkkkk----kkkk", "");

      Console.WriteLine(joeHas);
      Console.WriteLine(jackHas);
      Console.WriteLine(jimHas);
      Console.WriteLine(jasonHas);




Output:
Joe has 500 in his wallet.
Jack has 500 in his pocket.
Jim has 740 in his bag.
Jason has 900 in his car.
--------------------------
Joe has ${end}
Jack has $-500 in his pocket.
Jim has \${end}
Jason has $900 in his car.

推荐答案

使用以下替换模式： $ {start} $$$ {end}

双精度 $$ 转义 $ ，以便将其视为文字字符。第三个 $ 实际上是命名组 $ {end} 的一部分。您可以在MSDN 替换页面中了解其内容。

The double $$ escapes the $ so that it is treated as a literal character. The third $ is really part of the named group ${end}. You can read about this on the MSDN Substitutions page.

我会坚持使用上述方法。或者，您可以使用 Replace 重载，该重载接受 MatchEvaluator 并连接所需的内容，类似于以下内容：

I would stick with the above approach. Alternately you can use the Replace overload that accepts a MatchEvaluator and concatenate what you need, similar to the following:

jackHas = dollarInsertion.Replace(jackHas,
              m => m.Groups["start"].Value + "$" + m.Groups["end"].Value);

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