CODEWITHSUNDEEP
asp.net.netregexvalidationcharacter
JosephDoggie
JosephDoggie

Reputation: 1594

aspx reg expression validator: first character followed by optional second char

I need to form a regular expression (reg ex) for an .aspx program that validates one character followed by optional characters.

The first character is more strict, not allowing hyphen or space.

I had

^[A-Za-z0-9][A-Za-z0-9 -]{1,9}

which works, except there must be at least two characters (the limit is 9 chars total).

The .net code was as follows:

   controltovalidate="txt1" validationexpression="^[A-Za-z0-9][A-Za-z0-9 -]{1,9}"></ASP:REGULAREXPRESSIONVALIDATOR>

[Since asking the question, I've found that simply changing {1,9} to {0,9} accomplishes what I need, but I am retaining the question as possibly useful to others, especially the answer below]

I read that

^[A-Za-z0-9]([A-Za-z0-9 -])?{1,9}

might work as I'm grouping the chars after the first with parens and using a "?" as optional.

However, I really need to know if this is correct syntax before I move this code to production.

Furthermore, it fails an online reg expression validator.

Does anyone know if this will work for an aspx reg expression validator?

Upvotes: 1

Views: 101

Answers (1)

Eder
Eder

Reputation: 1884

Try the following: /^[A-Za-z0-9](?:[A-Za-z0-9 -]){1,8}$/

Working Demo @ regex101

Edit #1 (Explanation)

In your pattern ^[A-Za-z0-9]([A-Za-z0-9 -])?{1,9} the greedy quantifier aka {n,m} is preceded by the greedy quantifier aka ?, none of them are quantifiable tokens, So having a quantifier token preceded by another quantifier token is sematically incorrect.

In order to achieve your goal you must let that your second range of acceptable characters only allow 1 to 8 appearances: (?:[A-Za-z0-9 -]){1,8}

Upvotes: 1

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