How do I use RegEx to pick longest match?

Question

I tried looking for an answer to this question but just couldn't finding anything and I hope that there's an easy solution for this. I have and using the following code in C#,

String pattern = ("(hello|hello world)");
Regex regex = new Regex(pattern, RegexOptions.IgnoreCase);
var matches = regex.Matches("hello world");

Question is, is there a way for the matches method to return the longest pattern first? In this case, I want to get "hello world" as my match as opposed to just "hello". This is just an example but my pattern list consist of decent amount of words in it.

Answer 1

If you already know the lengths of the words beforehand, then put the longest first. For example:

String pattern = ("(hello world|hello)");

The longest will be matched first. If you don't know the lengths beforehand, this isn't possible.

An alternative approach would be to store all the matches in an array/hash/list and pick the longest one manually, using the language's built-in functions.