C# regular expression for American phone numbers without hyphens or parentheses?

Question

I'm looking for something that will validate the following:

13175551234
3175551234

but NOT validate:

1 (317) 531 1234
1-317-555-1234

Basically it should validate 10 or 11 digit phone numbers that can optionally begin with 1 and don't contain spaces, hyphens or parentheses. The area code should not be optional either.

How can I do this?

What language are you using? Regular expression syntax differs depending on the language. — Mark Byers, Feb 22 '11 at 19:45

score 3 · Accepted Answer · answered Feb 22 '11 at 19:39

3

That's actually pretty straightforward: ^1?\d{10}$

answered Feb 22 '11 at 19:39

Matt

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This one allows phone numbers (without 1 for long distance) that start with 1. For instance, 155-555-5555 is not a valid US phone number, but your regex will accept it as such. (Not downvoting, as it's a good effort.) – Ken White Feb 22 '11 at 19:47
2

Let's hope he is using javascript... Otherwhise ৩৩৩৩৩৩৩৩৩৩ will be a valid number! (\d catches non-euro-american digits, that is the Bengali Digit Three U+09E9 :-) ) (Javascript considers digits only 0-9) – xanatos Feb 22 '11 at 19:53
Personal research on this suggests that RegexOptions.ECMAScript seems to remedy this and enable Jscript compliance. Kudos for the regular expression gentlemen. No Bengali nationals will be using my SMS notifications service for any would be nefarious plots or terrorist operations. – whoblitz Feb 22 '11 at 20:46

score 1 · Answer 2 · edited May 23 '17 at 12:04

For something simple you could try this:

"^1?[0-9]{10}$"

Or slightly better:

"^1?[2-9][0-9]{9}$"

But this still matches incorrectly for some situations. For a better approach, see this answer:

A comprehensive regex for phone number validation

Depending on the programming language you are using may want to use \d instead of [0-9]. But please be aware that in C# \d can match any digits as defined by the Unicode standard. So it can include Chinese numerals and other numeric characters that are illegal characters in a phone number. However [0-9] works everywhere, even in Unicode aware languages.

score 0 · Answer 3 · answered Feb 22 '11 at 19:53

0

Try this:

^1?[^0-1][0-9]{9}$

It matches

13155551212
3155551212

It doesn't match

03155551212
10315551212
1055551212
11555551212

answered Feb 22 '11 at 19:53

Ken White

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That also matches 1৩155551212. – Mark Byers Feb 22 '11 at 20:06
1

@Mark Don't steal my preciousss Bengali Digit Three! Take another Bengali Digit!! :-) :-) – xanatos Feb 22 '11 at 20:08
@xanatos: Actually I was going to write `1W155551212` because that also matches, but I thought your Bengali digit three was much cooler. :) – Mark Byers Feb 22 '11 at 20:10
@Mark A present for you: ৪ (no, it isn't an eight... It's a PRECIOUS BENGALI DIGIT FOUR!!!) :-) – xanatos Feb 22 '11 at 20:11
@xanatos: That's neat! Great input to trick people into wasting several hours debugging why their regular expressions aren't working. :) – Mark Byers Feb 22 '11 at 20:13

C# regular expression for American phone numbers without hyphens or parentheses?

3 Answers3