Transforming a string using Regex C#

Question

i've been kicking my self for a while now with regex, and unable to find a proper solution. I've been trying to transform a string using Regex.Replace() method in C# which should prepend 0 to existing string if length is less than 5, the conversion might be as follow

Input String ----------- Output String
12345        ----------- 12345
123          ----------- 00123
123456       ----------- 123456

any help will be appreciated

Are these the actual input strings, or just the numbers contained within a bigger block of text? — Rhumborl, Feb 12 '15 at 14:28
does it have to be `Regex`? if not try this: http://stackoverflow.com/questions/3122677/add-zero-padding-to-a-string — Dave Becker, Feb 12 '15 at 14:28
Guys it has to be Regex... and '-' is not included in the input just used it for formatting — Mirza Talha, Feb 12 '15 at 14:31
Why use regex if framework already provides function specifically for that purpose ? — Mahesh, Feb 12 '15 at 14:32

Gerino · Answer 1 · 2015-02-12T14:41:04.107

2

You can use String.PadLeft: "1234".PadLeft(5, '0')

edited Feb 12 '15 at 14:41

answered Feb 12 '15 at 14:30

Gerino

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shouldn't it be `"1234".PadLeft(5, '0')` – Dave Becker Feb 12 '15 at 14:31
Whatever number he pleases ;) – Gerino Feb 12 '15 at 14:31
I take your point, but, OP stated "....if length is less than 5". (I think SO is making a pedant out of me!) : ) – Dave Becker Feb 12 '15 at 14:34
Changed it to correct number ;) – Gerino Feb 12 '15 at 14:41

score 1 · Answer 2 · answered Feb 12 '15 at 14:35

1

It can be like

var outputString = Regex.Replace(inputString, @"\d+", n => n.Value.PadLeft(5, '0'));

but you don't really need regex in this case.

answered Feb 12 '15 at 14:35

Nikitin Nikolay

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Regex is just overkill here. But OP wanted that way so ....:) – Mahesh Feb 12 '15 at 14:37
wow couldn't have figured out without ur help :P ... anyways i think there is no way left just to change the code – Mirza Talha Feb 12 '15 at 14:48

score 0 · Answer 3 · answered Feb 12 '15 at 14:29

0

You don't need any regex

if(str.Length < 5){
  for(var i = 0; i < 5 - str.length; i++)
      str = "0" + str;
}

The above is all you need. What you're doing is if the input string's Length is less than 5, you're just subtracting and looping, adding them.

answered Feb 12 '15 at 14:29

Amit Joki

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@MirzaTalha Why? Why place artificial restrictions on a solution? – mason Feb 12 '15 at 14:46
@mason because i don't want to change my code... it will result in re-deployment of the existing application – Mirza Talha Feb 12 '15 at 14:50
@MirzaTalha If you're asking for us to provide a regex, that means you're having to change the code anyways. Might as well use the proper tools for the job. Regex should only be used when there's absolutely no better option. – mason Feb 12 '15 at 14:51
@mason The regex is configurable from a configuration file, that is why i was asking for regex mate – Mirza Talha Feb 12 '15 at 15:10

Transforming a string using Regex C#

3 Answers3