Regular Expression Annotation Fails Despite Being Correct

Question

In my model I have the following:

[Required(ErrorMessage = "First name is required.")]
[Display(Name = "First Name")]
[MaxLength(50)]
[RegularExpression(@"/^[A-z]+$/", ErrorMessage = "Only alphabet characters are allowed.")]
public string FirstName { get; set; }

In the form it's failing the check no matter what I put in there. I want it to just make sure there are only letters, no numbers or special characters.

This is not a duplicate because the referenced post has nothing to do with data annotations. They're two different contexts.

Possible duplicate of [Regex to match only letters](http://stackoverflow.com/questions/3617797/regex-to-match-only-letters) — Pawel Maga, Jan 12 '17 at 21:07

score 2 · Accepted Answer · edited May 23 '17 at 12:34

2

You need to remove the regex delimiters (that are not used in .NET regex and are thus treated as literal slashes) and replace A-z with A-Za-z (see Why is this regex allowing a caret?).

Use

@"^[A-Za-z]+$"

edited May 23 '17 at 12:34

Community

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answered Jan 12 '17 at 21:06

Wiktor Stribiżew

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[Regular Expression to match only alphabetic characters](http://stackoverflow.com/questions/6067592/regular-expression-to-match-only-alphabetic-characters) – Sergey Berezovskiy Jan 12 '17 at 21:06
@SergeyBerezovskiy: The accepted answer [there](http://stackoverflow.com/questions/6067592/regular-expression-to-match-only-alphabetic-characters) is wrong. Besides, the `/.../` is a common regex writing form, in .NET, the `/` are parsed as literal symbols in the pattern. – Wiktor Stribiżew Jan 12 '17 at 21:08
Hmmm.. need to check – Sergey Berezovskiy Jan 12 '17 at 21:08
yep, I believe `/.../` is what really causing the problem in this case :) – Sergey Berezovskiy Jan 12 '17 at 21:11
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And `[A-z]` will cause another problem if OP does not use my suggestion. – Wiktor Stribiżew Jan 12 '17 at 21:11
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Also note `"(?i)^[a-z]+$"` would work (adds the case insensitive flag), or if you want to support languages other than English, `"^\p{L}+$"`. – p.s.w.g Jan 12 '17 at 21:13
I always use a-zA-Z pattern :) Now checked ASCII table and see that there is [ ] ^ between two ranges. – Sergey Berezovskiy Jan 12 '17 at 21:14
@p.s.w.g: To support Uncode, it should be `@"^\p{L}+$"` and to also support diacritics, `@"^[\p{L}\p{M}]+$"` – Wiktor Stribiżew Jan 12 '17 at 21:14
@WiktorStribiżew Woops yes, I forgot that slash – p.s.w.g Jan 12 '17 at 21:15

Regular Expression Annotation Fails Despite Being Correct

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