Question

I have a problem.

I want a user to be allowed to write everything you can SEE on a Swedish keyboard (not using a character map or similar). This means all English alphanumeric characters and åäö. The non-alphanumeric characters which is allowed is §½!"@#£¤$%&{/()[]=}?+\´`^ and so on.

My expression is:

[\wåäö§½!"@#£¤$%&/{()=}?\\\[\]+´`^¨~'*,;.:\-_<>|]

In C# it looks like this:

Regex allowedChars = new Regex("@[\\wåäö§½!\"@#£¤$%&/{()=}?\\\\[\\]+´`^¨~'*,;.:\\-_<>|]");

I check it with:

if (allowedChars.IsMatch(mTextBoxUserName.Text.Trim()))

The problem is that if i write a faulty character together with an allowed character the if statement think its a match. I want it to match it for the entire word. I tried adding a “+” at the end of the expression but then it never matched…

Any ideas?

Answer 1

Two things:

1. Your string erroneously has the @ character inside rather than before the string. This may have been a copy paste error, or it might not have been.

   // put the @ outside the ""
   new Regex(@"[\wåäö§½!""@#£¤$%&/{()=}?\\[\]+´`^¨~'*,;.:\-_<>|]");
   

2. You’re only checking that one of the allowed characters is present, rather than ONLY the allowed characters. You can use anchoring and repetition to solve this problem:

   // anchor using ^ and $, use []+ to ensure the string is ONLY made
   // up from that character class. Also move the - to be the last symbol
   // to avoid inadvertent ranging
   new Regex(@"^[\wåäö§½!""@#£¤$%&/{()=}?\[\]+´`^¨~'*,;.:\\_<>|-]+$");