Question

I know this stuff has been talked about a lot, but I’m having a problem trying to match the following…

Example input: “test test 310-315”

I need a regex expression that recognizes a number followed by a dash, and returns 310. How do I include the dash in the regex expression though. So the final match result would be: “310”.

Thanks a lot – kcross

EDIT: Also, how would I do the same thing but with the dash preceding, but also take into account that the number following the dash could be a negative number… didnt think of this one when I wrote the question immediately. for example: “test test 310–315” returns -315 and “test 310-315” returns 315.

Answer 1

Regex regex = new Regex(@"\d+(?=\-)");

\d+ – Looks for one or more digits

(?=\-) – Makes sure it is followed by a dash

The @ just eliminates the need to escape the backslashes to keep the compiler happy.

Also, you may want this instead:

\d+(?=\-\d+)

This will check for a one or more numbers, followed by a dash, followed by one or more numbers, but only match the first set.

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In response to your comment, here’s a regex that will check for a number following a -, while accounting for potential negative (-) numbers:

Regex regex = new Regex(@"(?<=\-)\-?\d+");

(?<=\-) – Negative lookbehind which will check and make sure there is a preceding -

\-? – Checks for either zero or one dashes

\d+ – One or more digits