How to write Regular expessions in asp.net? for Email Validator?

Question

I want to know the General formula for Writing Regular Expression?If any article can help Me.

Answer 1

Yes, start with the Regex class. And read lots of tutorials, like this one.

Answer 2

Regexes for email addresses are trickier than you'd think. Here's a good page to start: http://www.regular-expressions.info/email.html

A "complete" regex here: http://code.iamcal.com/php/rfc822/full_regexp.txt ;)

Answer 3

There isn't really a general formula. Regex is a non-trivial language for matching strings. There are plenty of books and tutorials available.

One of the better ways of learning regex is to use a piece of regex designer software, like this one.

Regexes for emails are tricky, but there are some good ones here: http://regexlib.com/DisplayPatterns.aspx

Answer 4

in .vb if you dont care about a postback....

Imports System.Text.RegularExpressions

valueStr = Regex.Replace(oldString, ",", ",@")

Another common way to do it is in javascript in your aspx page without a postback.

script type = "text/javascript"

function intChecker(field) {

    //use regular expressions to take out alphanumeric characters
    //and special characters such as !@#$ 
    //The reason I run the match before I run the replace is so that the
    //cursor doesn't jump to the end of the textbox unless it is a bad character
    var regExp2 = /[A-Za-z\.\!\@\#\$\%\^\&\*\(\)\,\?\:\;\_\-\+\=\~\/]/g;
    if (field.value.match(regExp2)) {
        field.value = field.value.replace(regExp2, '');
    }

}

/script

This will get you started with regex in vb. You will need to find the expression to validate the email address. Have fun!