Question

I am working on parsing the user provided input for a number which belongs to a specified pattern such as 199-234

where the

1. first component is 1
2. second component is 99
3. third component is 234

The user would provide just the first few digits or the entire string. I intend to parse each of the components out. The reg-ex that I have come up with is –

Regex regex = new Regex(@"(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3})");
var groups = regex.Match(input);

If I provide the input 199 , the reg-ex pattern breaks them into 3 groups instead of the expected 2.
Actual result is

1. first component is 1
2. second component is 9
3. third component is 9

How do I ensure that the inputs get correctly matched in this case?

Answer 1

Try the non-greedy version of the third group: \d{0,3}?

Regex regex = new Regex(@"(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3}?)");
var groups = regex.Match(input);

It also might help (for clarity’s sake) to bind the beginning and end of the strings (^ and $)

new Regex(@"^(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3}?)$");