C# Capturing the first match with regex

Question

I've got an input string that looks like this:

url=https%3A%2F%2Fdomain.com%2Fsale-deal%3Futm_source%3Dinsider-primary-action%3Dinsider-primary-action&utm_source=FB

or

url=https%3A%2F%2Fdomain.com%2Fsale&utm_source=FB&sub_id1=M12

the string sometimes has or non %3Futm_source

how to get link between url= and %3Futm_source% or &utm_source

Regex reg = new Regex(@"url=(https%3A%2F%2Fdomain.com[a-zA-Z0-9-_/%\.]+)%3Futm_source|&utm_source");
                    Match result = reg.Match(inPut);
Console.WriteLine(result.Groups[1].Value));

it always get from url= to &utm_source

Answer 1

You can use this

(?<=url=).*?(?=%3Futm_source|&amp;utm_source)

• (?<=url=) Positive look behind. matches url= .
• .* - Matches anything except new line.
• (?=%3Futm_source|&utm_source) - Positive look ahead. Matches %3Futm_source or &utm_source

Demo