Regular expressions on C#

hideway · November 27th, 2006, 01:12 PM

I'm trying to check if the string I'm getting from a web form is acceptable but it isn't working at all. I'm using these regular expressions on javascript without any visible problem.

Javascript version:

Code:

    var emailFilter1=/(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/;
    var emailFilter2=/^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/;
    var generalFilter=/^[a-zA-Z].[a-zA-Z0-9\-\._ ]+$/
    var generalFilter2=/^[a-zA-Z0-9\-\._ ]+$/

generalFilter.test(user.value)

C# version:

Code:

Regex filter1 = new Regex(@"/(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/");
                Regex filter2 = new Regex(@"/^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/");
                Regex generalFilter = new Regex(@"/^[a-zA-Z].[a-zA-Z0-9\-\._ ]+$/");
                Regex generalFilter2 = new Regex(@"/^[a-zA-Z0-9\-\._ ]+$/");

bool isTrue = generalFilter.IsMatch(user.Text);

isTrue is always set at false. I'm stuck on this for hours now. Any help is welcome. :)

hideway · November 27th, 2006, 01:16 PM

oh, btw. On the before the last I'm checking if the string begins with a letter and then if it has more any of these: - _ . a-z A-Z 0-9

Last one, I ignore the starting letter and just check for the acceptable chars.

RNedel · November 27th, 2006, 05:08 PM

hideway,

The first thing I notice when looking at your general filter is that it will NEVER work in C#. You have some mutually-exclusive commands within the pattern. For instance, the first two characters (/^) prevent the pattern from ever matching.

  / => Match a forward slash character.
  ^ => The next character should match the start of the string.

Well, if the first character of the match HAS to be a forward slash, then the second character can NEVER match the start of the string (by definition, it is the second character).

You make the same sort of error with the end of your general filter. You use the pattern ($/).

  $ => Matches the end of the string.
  / => Requires a forward slash AFTER the end of the string.

Without looking too terribly close at your whole filter, you might start by deleting the opening and closing forward slashes, leaving you with a general filter pattern of:

  ^[a-zA-Z].[a-zA-Z0-9\-\._ ]+$

By the way, it is hard to figure out what's wrong with your regular expression patterns when you don't supply any correct sample text strings to test-match with.

- Roger

Cheers.

- Roger Nedel