Regular Expression to validate Data

Question

In our application we need to check if a given string has only numbers and is of length 8 . How can we specify this conditions in a regular expression ?

Answer 1

bool isValid = Regex.IsMatch("YourInput", @"^\d{8}$");

Answer 2

Is it so difficult to write this regex? 3 persons have responded in 3 ways that are partially wrong. This clearly shows why regexes shouldn't ever be used! Because you can think you know how they work, and then they'll bite your ^a([az])\\1$ (it's a joke for persons that know regexes :-) ).

The regex is ^[0-9]{8}$ . You anchor the regex with ^ and $ at the beginning and the end of the string. You don't use fancy \\d , because the .NET Regex considers it to match 09E6 ০ BENGALI DIGIT ZERO (non european digits) unless you activate its ECMA mode ( RegexOptions.ECMAScript ). Javascript with \\d means only 0-9 digits. And if you really really want to use \\d , remember to escape the \\ or put a verbatim string literal sign before the string (the @"something" )

Answer 3

^[0-9]{8}$

Simple and clean. You set the acceptable value range, inside the ['s, and the number of hits inside the {'s. ^ and $ to specify start and end of string, to make sure you don't match sections of strings, containing 8 numbers, as Xanatos says.

Answer 4

Have you ever tried FilteredTextBox Demonstration in Ajax Control Toolkit?

It's pretty cool.