Regex Negative Lookbehind with spases on c#

i can't understand regex Negative Lookbehind..

I need not to catch '(this)' if there was a 'not' word some spaces before. For example:

... (this) - catch
... not(this) - not catch
... not (this) - not catch too, but it do

Please tell me where i am wrong, i can't make it work. My template :

(?<!\bnot\b)\s*(\(.*?this.*?\))

And (?<!...) can't understand something like (?<!\bnot\b\s*)

https://regex101.com/r/mK1yQ1/1

Solution

Well, you are using a wrong online regex tester, you need one supporting .NET regex syntax. Regex101.com does not support .NET regex syntax.

You may actually use

(?<!\bnot\b\s*)\(this\)

See this regex demo

Pattern explanation:

(?<!\bnot\b\s*) - check and fail the match if there is a
- \b - leading word boundary
- not - not literal substring
- \b - trailing word boundary
- \s* - zero or more whitespaces
\( - a literal ( symbol
this - a literal string this
\) - a literal ) symbol.

Note that this pattern does not match this in rtjtj bbg (this,and that). To make it match that this, you may add a ? (one or zero) quantifier after the last \) -> (?<!\bnot\b\s*)\(this\)?. You may further adjust the pattern.