Validation Regular Expression in ASP.NET

Question

In an HTML DOC I reported for a textbox the following validation code:

<asp:RegularExpressionValidator ID="revPhone" runat="server" 
            CssClass="validator" Display="Dynamic" ErrorMessage="Phone number" 
            ValidationExpression="((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}?|(\d{6.9})?" 
            ControlToValidate="txtPhone" >Use this format: 999-999-9999 or 999999 0r 999999999
 </asp:RegularExpressionValidator><br />

I would like to understand if this regular expression:

ValidationExpression="((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}?|(\d{6.9})?"

is correct to be able to enter one of the following values:

234-456-7890
234567
234567890

Because it returns me the error message if I enter:
234567890

Thank you I replaced the expression with the one you suggested: ValidationExpression="(\d{3}-\d{3}-\d{4})|\d{6,9}" but the problem remains. — Antony
– Antony, Commented Mar 24, 2020 at 10:35
The code: ValidationExpression="(((\d{3}) ?)|(\d{3}-))?\d{3}-\d{4}?" works properly but only if I enter 999-999-9999 Thank you — Antony
– Antony, Commented Mar 24, 2020 at 10:38
colinD: Yes I saw it and used it. But it doesn't work. I don't know what to say. Thank you — Antony
– Antony, Commented Mar 24, 2020 at 11:01

colinD · Accepted Answer · 2020-04-01 08:59:10Z

1

The start and end of the string delimiters are missing, which is why I thing the regex is not working.

^ is the start of the string, $ the end of it.

This should work:

^\d{3}-\d{3}-\d{4}$|^\d{6}$|^\d{9}$

Which means:

^\d{3}-\d{3}-\d{4}$ --> start, then 3 groups of digits with a '-' in the middle, then end
| --> or
^\d{6}$ --> start then 6 digits then end
| --> or
^\d{6}$ --> start then 9 digits then end

You can see it here: https://regex101.com/r/HgI3R5/2

Good website to test regex, includes reference of the tokens you can use and an explanation of the regex you're building.

answered Apr 1, 2020 at 8:59

colinD

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