Question about ,(?=(?:[^']*'[^']*')*[^']*$)

Question

C# Regex Split - commas outside quotes

var result = Regex.Split(samplestring, ",(?=(?:[^\"]*\"[^\"]*')*[^\"]*$)");

I have problems to understand how it works.

Specifically, I don't know what the * matches here?

",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)")
                     ^

Does it mean

there are 0 or more of (?=(?:[^\"]*\"[^\"]*')

update for a sample input

2,1016,7/31/2008 14:22,Geoff Dalgas,6/5/2011 22:21,http://stackoverflow.com,"Corvallis, OR",7679,351,81,b437f461b3fd27387c5d8ab47a293d35,34

Use the following code to test:

string samplestring = "2,1016,7/31/2008 14:22,Geoff Dalgas,6/5/2011 22:21,http://stackoverflow.com,\"Corvallis, OR\",7679,351,81,b437f461b3fd27387c5d8ab47a293d35,34";

Answer 1

It means that the group (?:[^']*'[^']*') is matched zero or more times.

,       // match one comma
(?=     // Start a positive lookAHEAD assertion
(?:     // Start a non-capturing group
[^']*   // Match everything but a single-quote zero or more times
'       // Match one single-quote
[^']*   // Match everything but a single-quote zero or more times
'       // Match one single-quote
)*      // End group and match it zero or more times
[^']*   // Match everything but a single-quote zero or more times
$)      // end lookAHEAD

Answer 2

You could check your regex and make your test on this website:

http://www.annuaire-info.com/outil-referencement/expression-reguliere/

;) have fun