正则表达式（C＃）：将\n替换为\r\n [英] Regex (C#): Replace \n with \r\n

问题描述

如何在C＃中使用正则表达式将\n的单个实例替换为\r\n（LF仅与CRLF一起使用）？

How can I replace lone instances of \n with \r\n (LF alone with CRLF) using a regular expression in C#?

对不起，如果这是一个愚蠢的问题，我是Regex的新手。

Sorry if it's a stupid question, I'm new to Regex.

我知道使用计划 String.Replace ，例如：

I know to do it using plan String.Replace, like:

myStr.Replace("\n", "\r\n");
myStr.Replace("\r\r\n", "\r\n");

但是，这是微不足道的，会破坏任何 \r + \r\n

However, this is inelegant, and would destroy any "\r+\r\n" already in the text (although they are not likely to exist).

推荐答案

这样做会吗？

[^\r]\n

基本上，它与以不为'\r'的字符开头的'\n'匹配。

Basically it matches a '\n' that is preceded with a character that is not '\r'.

如果要检测到它行也以单个 \n开头，然后尝试

If you want it to detect lines that start with just a single '\n' as well, then try

([^\r]|$)\n

哪个应该与 \n匹配，但仅与一行的第一个字符或 not 的第一个字符以'\r'

Which says that it should match a '\n' but only those that is the first character of a line or those that are not preceded with '\r'

由于您在重新弄乱行本身的定义， $可能无法很好地工作。但是我认为您应该明白这个想法。

There might be special cases to check since you're messing with the definition of lines itself the '$' might not work too well. But I think you should get the idea.

编辑： credit @Kibbee使用look-ahead显然会更好，因为它不会捕获匹配的前一个字符，也应有助于处理任何边缘情况。因此，这里有一个更好的正则表达式+代码变为：

credit @Kibbee Using look-ahead s is clearly better since it won't capture the matched preceding character and should help with any edge cases as well. So here's a better regex + the code becomes:

myStr = Regex.Replace(myStr, "(?<!\r)\n", "\r\n");

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