CODEWITHSUNDEEP
c#regex
leopik
leopik

Reputation: 2351

Match an email address if it contains a dot

I want to match any email address, that contains at least one . (dot) before the @ sign. The emails have already been validated, so the regex just needs to search for the ..

I have tried

Regex emailMatcher = new Regex(@"^[a-zA-Z\.']{1,}\.[a-zA-Z\.']{1,}@example\.com$");

But I know that emails can contain more characters than just a-zA-Z\.' so this won't cover all cases.

Any ideas on how to do it?

Thanks

EDIT: I'm not trying to validate emails, I already have the emails validated, I just need to select emails, that contain . before @ sign

Examples that would pass:

[email protected]
[email protected]

Examples that should pass, but wouldn't pass using my current regex

first.last(comment)@example.com

Upvotes: 5

Views: 3290

Answers (5)

hangy
hangy

Reputation: 10859

James' answer will probably give you the best performance. However, the IndexOf approach will not handle a quoted-string (ie. "[email protected]"@example.com, which is a valid address according to RCF 5322). To support that case, and if performance is not an issue, you could also use the following, which is a little bit more readable and verbose on what the intention of the LINQ query is:

emails.Select(m => new MailAddress(m)).Where(m => m.User.Contains('.')).ToList();

The overhead of building the MailAddress objects is pretty obvious, but this makes it really clear that you want those addresses that have a dot in the local part of the address.

Upvotes: 2

David Arno
David Arno

Reputation: 43254

LinQ could be used to both avoid a regex and to avoid calling IndexOf() twice on ".":

var dottyEmails = (from email in emails 
                   let dotIndex = email.IndexOf(".")
                   let atIndex = email.IndexOf("@")
                   where dotIndex >= 0 && dotIndex < atIndex
                   select email).ToList();

Upvotes: 2

James
James

Reputation: 82096

You could do this without a regex

Func<string, bool> dotBeforeAt = delegate(string email) 
{ 
    var dotIndex = email.IndexOf(".");
    return dotIndex > -1 && (dotIndex < email.IndexOf("@"));
};
...
emails.Where(dotBeforeAt).ToList();

Try it out

Upvotes: 7

karthik manchala
karthik manchala

Reputation: 13640

You can use lookahead.. for this purpose..

(?=\.).+@

Explanation:

  • Look forward for a dot, followed by any characters followed by @

Edit: To match the email with the above criteria.. you can use 

.+(?=\..+@).+

See DEMO

Upvotes: 2

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726589

I just need to select ones, that contain dot before @ sign

Then there is no point to build a regex that matches valid e-mail addresses. All you need is a regex that sees that there is a dot in front of the @ sign:

(?<=[.][^@]*)@

(?<=[.][^@]*) is a positive lookbehind construct. It ensures that the @ sign following it is matched only when there is a dot [.] followed by zero or more non-@ characters in front of it.

Upvotes: 3

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