How can I escape characters (, ), [, ], *, _, with \ without changing link construction: []()-CodePudding

I have a problem, for example I have a text:

input = "text, *text*, text, text, (text), [text], [some_text with _*](http://.....) *text*, text, text, (text), [text]"

I'm trying to replace characters '_', '*', '[', ']', '(', ')' to '\_', '\*' etc.

I'm writing:

pattern = @"(?<!\[(?<text>.*)\]\((?<url>.*))([[\]\(\)*_])";

input = Regex.Replace(input, pattern, @"\$1");

System output: "text, \*text\*, text, text, \(text\), \[text\], \[some\_text with \_ \* \]\(http://.....) \*text\*, text, text, \(text\), \[text\]"

How to make sure that the design of the link []() doesn't change? i.e. it would look like:

desired output:"text, \*text\*, text, text, \(text\), \[text\], [some\_text with \_ \*](http://.....) \*text\*, text, text, \(text\), \[text\]"

CodePudding user response：

You need to match and capture the markdown link part, and just match the chars you need to escape, and then use a match evaluator in the replacement part:

var input = "text, *text*, text, text, (text), [text], [some_text with _*](http://.....) *text*, text, text, (text), [text]";
var pattern = @"(\[[^][]*]\([^()]*\))|[][()*_]";
Console.WriteLine(Regex.Replace(input, pattern, m => 
    m.Groups[1].Success ? m.Groups[1].Value : $@"\{m.Value}"));

See the C# demo. Details:

(\[[^][]*]$[^()]*$) - Capturing group 1 matching [, then zero or more chars other than [ and ] (with [^][]*), then a ] char, (, then zero or more chars other than ( and ) (with [^()]*) and then a ) char
| - or
[][()*_] - a character class that matches: ] (note it is not escaped because it is the first char in the character class), [, (, ), * or _ chars.

The m => m.Groups[1].Success ? m.Groups[1].Value : $@"\{m.Value}" replacement replaces the match found with Group 1 value if Group 1 matched, else, the replacement is the match value (the special char defined in the character class) with a \ prepended.