Regex works in JavaScript but not in C#

Question

I have a regex that I use to validate emails and in JavaScript it looks like this:

function CheckIfValidEmail(TheEmail) {

    return /^([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22))*\x40([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d))*$/.test(TheEmail);
}

I didn't create that regex, I found it online. I want to use the same regex in my C# code with an extension method like this:

public static bool IsValidEmailAddress(this string TentativeEmailAddress)
{
    string Pattern = "@/^([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22))*\x40([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d))*$/";
    Regex regex = new Regex(Pattern);
    
    return regex.IsMatch(TentativeEmailAddress.ToLower());
}

Basically, I copy-paste the regex in the C# code expecting it to work but instead I get an error message that says parsing 'the regex' - Too many )'s.

What do I need to change to make this work?

holy sweet lord. let me suggest you try something like this: composableregex.apphb.com to help you break this kind of thing up. full disclosure, it's a site i wrote to build composable regex and help manage that. — devshorts
– devshorts, Commented Feb 21, 2014 at 0:31
I know I'll need a new pair of glasses, that regex broke mine ;-) — Luc Morin
– Luc Morin, Commented Feb 21, 2014 at 0:32
@devshorts: is your site still available? That link doesn't work for me. — halfer
– halfer, Commented Mar 28, 2023 at 10:36
@halfer its not but the github is github.com/devshorts/ComposableRegex — devshorts
– devshorts, Commented Apr 7, 2023 at 21:40

Szymon · Accepted Answer · 2014-02-21 00:33:57Z

7

I think you misplaced @ which should be before " in C# so that you don't have to double backslashes. Also, you don't need to put regex in / ... /

string Pattern = @"^ ... $";

answered Feb 21, 2014 at 0:33

Szymon

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