Regex reject string if it contains only certain characters

Question

I am trying to achieve the following using regex in C# in .Net application

I need to restrict strings which contains 'ONLY' these three special characters namely #,@ and %. Any other character is allowed

some examples

ab#c - allowed

abc#@ - allowed

#%abc - allowed

#@% - not allowed

##@ - not allowed

What I tried ^(?!(#|@|%)+$) But it doesn't seem to work as expected. Where am I going wrong ?

I am using data annotations on the property, so I am looking for a regex pattern that can exclude the incorrect input strings. I cannot use the Regex.IsMatch() function.

Clarification: My string should accept any characters. The only case it should fail is when the input string only has #,@ or %.

If you consider `$` and word chars as "valid" , you need `^[#@%$]*[\w$][\w$#@%]*$`. Please explain your requirements. — Wiktor Stribiżew, Aug 23 '21 at 07:49
So the case is my string can accept any character. The only restriction I want in place is to restrict strings that have only #, @ or %. — wickjon, Aug 23 '21 at 07:52

score 0 · Answer 1 · edited Aug 23 '21 at 07:59

0

This isn't elegant but does the job I think: ^[\w#@%]*\w+[\w#@%]*$

Works for your examples

I'm taking "non-special" characters to mean \w.

edited Aug 23 '21 at 07:59

Enigmativity

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answered Aug 23 '21 at 07:28

Chris D

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`^[#@%]*\w[\w#@%]*$` is more optimal. Note it includes `_`. – Wiktor Stribiżew Aug 23 '21 at 07:32
@WiktorStribiżew In case of %$$ it fails. % is an invalid, but $ is acceptable. If the string contains at least one valid character, it should be acceptable. – wickjon Aug 23 '21 at 07:47
@wickjon Then this answer is wrong. – Wiktor Stribiżew Aug 23 '21 at 07:48

Regex reject string if it contains only certain characters

1 Answers1