Regex to prevent textbox from accepting email addresses

Question

What is a regular expression that I can use to prevent a textbox from accepting an email address?

Good validation doesn't reject things but specifies what _is_ allowed. Will your texts contain '@' ? — Henk Holterman, Feb 02 '11 at 13:41
An additional criteria would be: Do you mean that the whole string cannot be an email address or that it can't contain an email address? — Lazarus, Feb 02 '11 at 13:44
And do you have max/min length, what char sets, spaces allowed? — Henk Holterman, Feb 02 '11 at 14:00
I'd suggest reading this question with it's answers: [What is the best regular expression for validating email addresses?](http://stackoverflow.com/questions/201323/what-is-the-best-regular-expression-for-validating-email-addresses) — Hans Olsson, Feb 02 '11 at 14:08

score 4 · Answer 1 · answered Feb 02 '11 at 13:39

4

Simply use a regex that is for an email address and check there are no matches.

answered Feb 02 '11 at 13:39

Jamiec

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score 4 · Accepted Answer · edited Mar 20 '14 at 05:56

4

Regex emailregex = new Regex("([0-9a-zA-Z]([-\.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})");
String s = "johndoe@example.com";
Match m = emailregex.Match(s);
if (!m.Success) {
   //Not an email address
}

However, be very warned that others much smarter than you and I have not found the perfect regex for emails. If you want something bulletproof then stay away your current approach.

edited Mar 20 '14 at 05:56

jdphenix

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answered Feb 02 '11 at 13:47

NakedBrunch

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If you want a more comprehensive email address matching regex (RFC compliant) then try this ((?>[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+\x20*|"((?=[\x01-\x7f])[^"\\]|\\[\x01-\x7f])*"\x20*)*(?\.?[a-zA-Z\d!#$%&'*+\-/=?^_`{|}~]+)+|"((?=[\x01-\x7f])[^"\\]|\\[\x01-\x7f])*")@(((?!-)[a-zA-Z\d\-]+(?) Short of verifying the domain, it covers most eventualities. More like this at http://www.regexlib.com – Lazarus Feb 02 '11 at 13:56

score 2 · Answer 3 · answered Feb 02 '11 at 13:45

2

Read How to Find or Validate an Email Address and then check for no matches or negate the expression.

answered Feb 02 '11 at 13:45

Nick Jones

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score 1 · Answer 4 · edited Oct 28 '12 at 16:39

1

It should be like this:

Regex emailRegex = new Regex(@"([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]    {1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})");
Match m = emailRegex.Match(this.emailAddress);
if (!m.Success) {
    MessageBox.Show("Email address is not correct");
} else { 
    Application.Exit();
}

edited Oct 28 '12 at 16:39

Aoi Karasu

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answered Oct 28 '12 at 16:18

Evgeny

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Regex to prevent textbox from accepting email addresses

4 Answers4