Check if a string only contains the characters > or < or -

Question

What I need is to check if a string only contains the characters > or < or -.

So I thought using a RegEx for this, and I found an SO question with the exact same problem, and it has an answer (not the accepted one but the answer with regex)

This is the SO question : String contains only a given set of characters

So I modified the expression in this question to fit my needs like this :

static readonly Regex Validator = new Regex(@"^[><- ]+$");

and I call it like this ;

Validator.IsMatch(testValue)

But it's throwing the error

x-y range in reverse order

There are lots of question on SO about this error but I cant find or understand the answer I need.

So what am I doing wrong with this RegEx?

No need escaping the hyphen if you [place the hyphen at the right place inside the character class](https://stackoverflow.com/a/4068725/3832970). — Wiktor Stribiżew, Sep 07 '18 at 08:08
*Linq* alternative: `bool result = testValue.All(c => c == '<' || c == '>' || c == '-');` — Dmitry Bychenko, Sep 07 '18 at 08:08

score 1 · Answer 1 · answered Sep 07 '18 at 08:06

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^[-<>]+$ "-" must come first in C# regex

answered Sep 07 '18 at 08:06

Prodigle

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Thanks, the answer is simple it was just never explained simple in most so answers – GuidoG Sep 07 '18 at 08:20
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`-` symbol has a special meaning and should be escaped when we want to treat it litteraly, e.g. `[0-9]` is a range of characters `0, 1, 2, ..., 9` while `[0\-9]` means exactly `0`, `-` or `9` character. – Crozin Sep 07 '18 at 08:31

score 0 · Accepted Answer · edited Sep 07 '18 at 08:26

0

Escape - within character groups. ([0-9] means "zero to nine" and not "zero, dash or nine")

edited Sep 07 '18 at 08:26

Paolo

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answered Sep 07 '18 at 08:02

dognose

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how does one escape in regex ? – GuidoG Sep 07 '18 at 08:02
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new Regex(@"^[><\- ]+$"); – DiabloSteve Sep 07 '18 at 08:03
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@DiabloSteve make that an answer, not a comment :/ – hellow Sep 07 '18 at 08:03
generally `\-` but depending on the language you then need to escape the `\ ` as well within String-Objects: `\\-` – dognose Sep 07 '18 at 08:03
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@dognose The @ before the string in C# means that escaping is automatic. They're called [verbatim string literals](https://stackoverflow.com/questions/556133/whats-the-in-front-of-a-string-in-c) – Nick is tired Sep 07 '18 at 08:06
Thanks, the answer is simple it was just never explained simple in most so answers – GuidoG Sep 07 '18 at 08:20
You only need to escape the `-` depending on its position, and according to the contents of the character set. – Paolo Sep 07 '18 at 08:27

Check if a string only contains the characters > or < or -

2 Answers2