Email expression validation problem

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Hi Friends,

I have two expression to validate the email ID
#1 "^[a-zA-Z0-9_\\+-]+(\\.[a-zA-Z0-9_\\+-]+)*@[a-zA-Z0-9-]
+(\\.[a-zA-Z0-9-]+)*\\.([a-zA-Z]{2,4})$"

#2 "Regex.IsMatch(viewmodel.Email, @"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$)"

The Problem is #1 validation expression always successful. But #2 validation expression is fail in some case.

1. why expression #2 is fail
2. Which expression ( #1 and #2) is best to use

Please help in this issue.

Thanks,
Shanmuga Raja

What I have tried:

I dont Know why "Regex.IsMatch(viewmodel.Email, @"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$)" gets fail.

Posted 28-Aug-16 22:39pm

shanmugarajaa

Updated 12-Sep-22 17:42pm

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OriginalGriff · Answer 1 · 2016-08-28T22:49:00

I dont Know why "Regex.IsMatch(viewmodel.Email, @"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$)" gets fail.

Mismatched brackets.
The expression you pass to Regex contains a spurious ')' at the end which the expression evaluator doesn't understand.

But...I wouldn't use a regex for this: you can get long TLDs which don;t fit in three of four characters: ".museum" for example, so restricting TLD to 2 or 4 characters is a bad idea. Also, a domain can contain '.' as either part of the name: "mobile.mydomain.com" or part of the "country code": "mydomain.co.uk" so you need to allow for that.

Microsoft recommend using the MailAddress Class (System.Net.Mail)[^] constructor to check for valid names: How to: Verify that Strings Are in Valid Email Format[^] - see the NOTE section.