Question

Just come across the following line of code and having a hard time finding documentation for it, is it a lambda expression? What does this do?

temp = Regex.Replace(url, REGEX_COOKIE_REPLACE,match => cookie.Values[match.Groups["CookieVar"].Value]);

Specifically interested in the =>.

Answer 1

If you look at the documentation for Replace, the 3rd argument is a MatchEvaluator:

http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.matchevaluator.aspx

This is a delegate that takes a Match as an argument and returns the string to replace it with. Your code is defining a MatchEvaluator using a lambda expression:

match => cookie.Values[match.Groups["CookieVar"].Value]

Here, for each match that the Regex finds, a value is being looked up in the cookie.Values dictionary and the result is being used as the replacement.