Question

I have a string like this:

• blah blah blah_0123

So basically i need a regular expression to get those 4 numeric values after the _ delimiter. I’m sure it’s super simply but Regex looks like a foreign language to me!

Answer 1

That would be this regular expression:

_([0-9]+)

(Capture group 1 holds the number.)

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Or if your engine supports lookbehinds (which as far as I remember is not the case for C#):

(?<=_)[0-9]+

(Capture group 0 holds the number.)

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The (...) denotes a catch group. In your match object you can then either access them by their index via yourMatch.Groups[index].Value or if you named your catch groups via (?<name>...) by their name like yourMatch.Groups[name].Value. The value will then hold whatever was matched by that particular group’s sub-expression (in your case the 4-digit number).

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Also if you only want the regex to match if those are exactly 4 numeric characters,
then replace the + with {4}\b

_{Edit: As Alan Moore correctly pointed out those are called “capture group”, not “catch group”. I need more sleep.}