Detect Two Consecutive Single Quotes Inside Single Quotes

Question

I'm struggling to get this regex pattern exactly right, and am open to other options outside of regex if someone has a better alternative.

The situation: I'm basically looking to parse a T-SQL "in" clause against a text column in C#. So, I need to take a string value like this: "'don''t', 'do', 'anything', 'stupid'"

And interpret that as a list of values (I'll take care of the double single quotes later):

• "don''t"
• "do"
• "anything"
• "stupid"

I have a regex that works for most cases, but I'm struggling to generalize it to the point where it will accept any character OR a doubled-up single quote inside my group: (?:')([a-z0-9\s(?:'(?='))]+)(?:')[,\w]*

I'm fairly experienced with regexes, but have rarely, if ever, found a need for look-arounds (so downgrade my assessment of my regex experience accordingly).

So, to put this another way, I'm wanting to take a string of comma-delimited values, each enclosed in single quotes but can contain doubled single quotes, and output each such value.

EDIT Here's a non-working example with my current regex (my problem is I need to handle all characters in my grouping and stop when I encounter a single quote not followed by a second single quote):

"'don''t', 'do?', 'anything!', '#stupid$'"

Answer 1

If you still think about a regex-based solution, you can use the following regex:

'(?:''|[^'])*'

Or an "un-rolled" version suggested by @sln:

'[^']*(?:''[^']*)*'

See demo

It is fairly simple, it captures double single quotation marks OR anything that is not a single quotation mark. No need using any look-behinds or look-aheads. It does not take care of any escaped entities, but I do not see this requirement in your question.

Moreover, this regex will return matches that are easy to access and deal with:

var text = "'don''t', 'do', 'anything', 'stupid'";
var re = new Regex(@"'[^']*(?:''[^']*)*'"); // Updated thanks to @sln, previous (@"'(?:''|[^'])*'");
var match_values = re.Matches(text).Cast<Match>().Select(p => p.Value).ToList();

Output: