Question

I’m having trouble building a regular expression because I’m really a noob to the subject.

The goal is to validate ‘range’ expressions from the user input, like this:

• 20-30 (between 20 and 30)
• 11,12 (2 and 4)
• -10 (smaller than 10)
• 80- (larger than 80)

or combinations of any number of those, like:

-10,11,12,20-30,80-

I’m already able to parse the different components from a string like this using the following
regular expressions (and calling .GetMatches()):

var rangeRegex = new Regex(@"\d+(\.\d+)?-\d+(\.\d+)?");
var smallerThanRegex = new Regex(@"(?<![\d\.])-\d+(\.\d+)?");
var greaterThanRegex = new Regex(@"\d+(\.\d+)?-(?!\d)");

I’m just not sure on how to combine them into a big Regex that can be used to validate whether a string is a valid ‘range expression’.

Is there anyone who knows how to do this without wasting an entire week on it (like I would)? Thank you very much in advance!

Answer 1

This would be the regex to check the syntax, it has no ideas about the semantics of the string!

^(?<=\D|^)(?:\d+(?:\.\d+)?-\d+(?:\.\d+)?|-\d+(?:\.\d+)?|\d+(?:\.\d+)?-|\d+(?:\.\d+)?)(?:,(?:\d+(?:\.\d+)?-\d+(?:\.\d+)?|-\d+(?:\.\d+)?|\d+(?:\.\d+)?-|\d+(?:\.\d+)?))*(?=\D|$)$

See it here on Regexr

But splitting on the commas like Guffa suggested would be the better solution (+1)!