An invalid regex pattern

Question

I have a piece of code in c# that checks, if a value is a valid regex pattern.

Code is straight forward:

   try    {       System.Text.RegularExpressions.Regex.IsMatch("", pattern);    }    catch (Exception ex)    {        return "pattern matches must be a valid regex value";    } 

I'm trying to test if it works correctly, but I can't find an invalid regex pattern.

Any suggestions?

Answer 1

This is invalid...

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You can also test the validity of regular expressions in real-time at http://regexhero.net/tester/

By the way, you don't actually have to test the regular expression against a string to see if it's valid. You can simply instantiate a new Regex object and catch the exception.

This is what Regex Hero does to return a detailed error message...

public string GetRegexError(string _regexPattern, RegexOptions _regexOptions) {     try     {         Regex _regex = new Regex(_regexPattern, _regexOptions);     }     catch (Exception ex)     {         return ex.Message;     }      return ""; }