regex to allow only single digit or two digit numbers and comma in C#

Question

I searched internet and even followed the documentation of RegEx but unable to solve the issue. I want to validate single digit or double digit number. It should only accept

Use Case1: string sDate= ",01,23,05,1,28,25";

Use Case1: string sDate= ",01,23,05,1,28,25,";

Use Case1: string sDate= "01,23,05,1,28,25,";

Use Case1: string sDate= "01,23,05,1,28,25";

It should not accept anything i.e. no decimal, characters, special character except comma. I have written a code in C#

string stDate= ",01,23,05,1,28,25";

if (!string.IsNullOrEmpty(sDate))

            {
                Regex r = new Regex(@"^(\d+[,]\d*|\d*[,]\d+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase); 
                if (r.IsMatch(sDate))
                {
business logic
}
}
else
{
//business logic
}

I need to know where I"m going wrong. When I'm entering a alphabet in the string it is accepting it even. Any help would be highly appreciated. enter code here enter code here

For just validation - alteration of @WiktorStribiżew's - `^,?\d{1,2}(?:,\d{1,2})*,?$` To also get the matches - `^,?(\d{1,2})(?:,(\d{1,2}))*,?$` Test them here: http://regexstorm.net/tester — jimnkey, May 07 '21 at 19:06

The fourth bird · Answer 1 · 2021-05-07T19:29:37.460

1

To match optional repetitions of 1 or 2 digits where the comma can be at the start, end or in between, you can use:

^,?\d\d?(?:,\d\d?)*,?$

^ Start of string
,?\d\d? Match optional comma, a digit and optional digit
(?:,\d\d?)* Match 0 or more repetitions of a comma, digit and optional digit
,? Match optional comma
$ End of string

See a regex demo

edited May 07 '21 at 19:29

answered May 07 '21 at 19:10

The fourth bird

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score 0 · Answer 2 · answered May 07 '21 at 18:16

Looks like new Regex(@"^(,\d{1,2})+$") would work for you.

Your regex of ^(\d+[,]\d*|\d*[,]\d+)$ starts out by expecting one or more digits through \d+ followed by a mandatory comma, followed by any number of digits through \d* OR any number of digits again.

Sites like this are great for testing and practicing regexes. The site actually tests php but there is no significant difference.

score 0 · Answer 3 · answered May 07 '21 at 19:37

Use

Regex r = new Regex(@"\A,?[0-9]+(?:,[0-9]+)*,?\z", RegexOptions.Compiled);

See regex proof.

Relevant posts:

EXPLANATION

--------------------------------------------------------------------------------
  \A                       the beginning of the string
--------------------------------------------------------------------------------
  ,?                       ',' (optional (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  [0-9]+                   any character of: '0' to '9' (1 or more
                           times (matching the most amount possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    ,                        ','
--------------------------------------------------------------------------------
    [0-9]+                   any character of: '0' to '9' (1 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )*                       end of grouping
--------------------------------------------------------------------------------
  ,?                       ',' (optional (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  \z                       the end of the string

regex to allow only single digit or two digit numbers and comma in C#

3 Answers3