Replace a pattern that is within another pattern

Question

I want to be able to replace a line break (actually remove) but only if they exist within quotes.

The string below should have the line breaks in bold removed as they are inside quotes:

eg - This is the target string "and I \r\n want some" line "breaks \r\n" to be removed but not others \r\n. Can I do that?

See image below for regex pattern. I can isolate the quotes that have line breaks in them.

Now I want to be able to find the pattern \r\n within these matches and replace them, while leaving \r\n outside of quotes alone. enter image description here

Don't post screenshots of text, we can't copy+paste that.

Blorgbeard
– Blorgbeard

2015-05-04 22:56:37 +00:00
Commented May 4, 2015 at 22:56 — Blorgbeard
– Blorgbeard, Commented May 4, 2015 at 22:56

Wiktor Stribiżew · Accepted Answer · 2015-05-04 23:08:13Z

2

You can use the variable-width look-arounds in C#:

(?<="[^"]*)\\r\\n(?=[^"]*")

See demo on RegexStorm.net (regex101 does not support .NET regex).

In case you want to remove actual whitespace, you can use

(?<="[^"]*)[\r\n]+(?=[^"]*")

Sample code:

var rx = new Regex(@"(?<=""[^""]*)[\r\n]+(?=[^""]*"")");
var removed = rx.Replace("This is the target string \"and I \r\n want some\" line \"breaks \r\n\" to be removed but not others \r\n. Can I do that?", string.Empty);

Output (only 1 linebreak remains):

This is the target string "and I  want some" line "breaks " to be removed but not others 
. Can I do that?

edited May 4, 2015 at 23:08

answered May 4, 2015 at 22:58

Wiktor Stribiżew

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