Question

I have such string:

Text [City 1 || Location] text [Population] 
|| Text [City 2 || Location] text [Population]

I need regex which replace || just within [] with ==.

So i must be:

Text [City 1 == Location] text [Population] 
|| Text [City 2 == Location] text [Population]

I wrote this regex:

str = Regex.Replace(str, @"\[(.*?)\|\|(.*?)\]", "[$1==$2]");

But it replaces all || with ==.

How to fix it?

Answer 1

You should be able to avoid matching everything and only get the ‘||’ like that:

str = Regex.Replace(str, @"(?<=\[[^\[\]]*)\|\|(?=[^\[\]]*\])", "==");

So what is happening here?

(?<=\[[^\[\]]*) this is a zero width look behind that matches ‘[‘ and any character following it, other than ‘[‘ or ‘]’

\|\| this matches the actual ‘||’

(?=[^\[\]]*\]) this is a zero width look ahead that matches any character other than ‘[‘ or ‘]’, followed by ‘]’