Check for specific characters in string with regex

Question

Suppose I have a group of unwanted characters & " > < { } ( ) and I want to validate that a given string does not contains those characters, for now I wrote function like:

bool IsStringValid(string s){
  if(s.Contains("&")| s.Contains(">")...)
    return false;
return true;
}

How can I write it more elegant? for example in regex?

You could create a `HashSet` of the undesired characters then just do `return s.All(c => !undesired.Contains(c));` — juharr, Oct 07 '18 at 18:33
Btw you should use ||, not | https://stackoverflow.com/questions/35301/what-is-the-difference-between-the-and-or-operators — Antonín Lejsek, Oct 08 '18 at 01:30

score 2 · Answer 1 · answered Oct 07 '18 at 18:32

2

Regex is always your friend.

Regex validationRegex = new Regex(@"^[^&""><{}\(\)]*$");

bool IsStringValid(string s) => validationRegex.IsMatch(s);

answered Oct 07 '18 at 18:32

V0ldek

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score 2 · Accepted Answer · answered Oct 07 '18 at 18:37

2

bool isValid =  !Regex.IsMatch(input, "[&\"><{}()]+");

But however I recommand you do it without regex:

bool isValid = !"&\"><{}()".Any(c=> input.Contains(c));

answered Oct 07 '18 at 18:37

Ashkan Mobayen Khiabani

32,319
30
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Check for specific characters in string with regex

2 Answers2