C# Regex for 0-100

Question

I have a field on my c# mvc model to hold percentage - I want to use RegEx data annotation to validate that the field only contains values of 0-100

I seen a similar Regex here - ^([1-9][0-9]{0,2}|1000)$ - that matches values 1-1000 - I am not sure of the correct ammendment to make it fit for my scenario?

I tried something like below ^([0-9][0-9]{0,2}|100)$ but not working as expected?

^([0-9][0-9]{0,1}|100)$ and ^([1-9][0-9]?|100)$ both should work — vikas, Aug 19 '14 at 09:30
@vikas first option would validate value 01, which may not be what OP is after. Second option does not validate value 0. — Dialecticus, Aug 19 '14 at 09:38
Do you know `RangeValidator`?http://msdn.microsoft.com/ja-jp/library/system.web.ui.webcontrols.rangevalidator(v=vs.110).aspx — Jumpei, Aug 19 '14 at 09:38
[This](http://stackoverflow.com/q/22130429) might also be a good read. — HamZa, Aug 19 '14 at 09:45
*Some people, when confronted with a problem, think “I know, I'll use regular expressions.” Now they have two problems.* -- Jamie Zawinski — J..., Aug 19 '14 at 10:40

score 5 · Answer 1 · answered Aug 19 '14 at 09:31

5

Why do you want to validate it using a regex? I think it would be easier to just use .TryParse and a range check:

bool Validate(string input) {
  int x;
  return int.TryParse(input, out x) && x >= 0 && x <= 100;
}

Also more readable if you ask me …

answered Aug 19 '14 at 09:31

knittl

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@AvinashRaj I mean they constitute an inappropriate, albeit technically correct, solution to the problem. You can describe a correct technique for using a chainsaw to open a tin of soup, but it remains nevertheless an unsuitable tool (and approach) for the job. – J... Aug 19 '14 at 09:35

Avinash Raj · Accepted Answer · 2014-08-19T10:43:01.687

4

You could use the below pattern to match the digits from 0 to 100,

^(?:100|[1-9]?[0-9])$

DEMO

Explanation:

^ Asserts that we are at the start.
(?:) Non-capturing group which only does a matching operation.
100 Matches the string 100.
| Logical OR operator used to OR two regexes.
[1-9]? Matches one of any digit from the range 1 to 9. ? after the character class makes it optional.
[0-9] Matches one of any digit from the range 0 to 9.
$ Asserts that we are at the end of the line.

edited Aug 19 '14 at 10:43

answered Aug 19 '14 at 09:30

Avinash Raj

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+1, Though the shortest approach would be `^(?!0)\d{3}$`. – Unihedron Aug 19 '14 at 09:59
2

This solution is in excess of 500% more computationally intensive than a simple `TryParse` and range check. Don't write validation code like this. It's ugly, nonintuitive, hard to read, and incredibly inefficient. There is no sensible reason to choose regex to solve this problem. – J... Aug 19 '14 at 10:22
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@J... [There is.](https://www.thc.org/root/phun/unmaintain.html) – Unihedron Aug 19 '14 at 10:40
@J... - I am wanting to make use of Data Annotations above the property in Question - hence using RegEx – Ctrl_Alt_Defeat Aug 19 '14 at 12:38
@Ctrl_Alt_Defeat There is a range attribute you can use that is rather more appropriate - again, why regex? – J... Aug 19 '14 at 12:49
@J... I think originally I had used Range but my requirement for percentage field is whole numbers onlly - I belive Range allowed 2.5 for example which I did not want – Ctrl_Alt_Defeat Aug 19 '14 at 21:22
@Ctrl_Alt_Defeat if it is an integer property then it cannot have a non-integer component. – J... Aug 19 '14 at 22:01

score 2 · Answer 3 · answered Aug 19 '14 at 09:43

2

If the percentage field on your model is of type int, you could more easily use the Range annotation:

[Range(0, 100)]
public int Percentage { get; set; }

answered Aug 19 '14 at 09:43

WeSt

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npinti · Answer 4 · 2014-08-19T09:36:46.257

0

Something like so should work: ^([0-9]{1,2}|100)$. That being said, please refrain from using regular expressions for number evaluation. You should use numeric operators for this purpose.

edited Aug 19 '14 at 09:36

answered Aug 19 '14 at 09:30

npinti

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This does not validate value 0. – Dialecticus Aug 19 '14 at 09:35
@Dialecticus: Sorry my bad. Should be fixed now. – npinti Aug 19 '14 at 09:37
Right, but now regex will validate value 01, which may not be what OP was after. – Dialecticus Aug 19 '14 at 09:39

score 0 · Answer 5 · answered Aug 19 '14 at 09:31

0

You can do it like this:

^(([1-9]\d?)|100)$ This would ensure that

There is at least one digit

That multi-digit numbers start in a digit other than zero

That the only allowed three-digit number is 100.

answered Aug 19 '14 at 09:31

Jay Nirgudkar

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This does not validate value 0. – Dialecticus Aug 19 '14 at 09:36
just change the 1 to 0.. it should work fine... :) cheers n vote please.. – Jay Nirgudkar Aug 19 '14 at 09:47
No. Wont upvote current incorrect answer. And if I replace 1-9 with 0-9 value 01 would be validated, which may not be what OP is asking for. – Dialecticus Aug 19 '14 at 10:33

score 0 · Answer 6 · answered Aug 19 '14 at 09:31

0

This will work:

^([1-9]?[0-9]|100)$

answered Aug 19 '14 at 09:31

arco444

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C# Regex for 0-100

6 Answers6