Validating e mail

^ #start of the line [_A-Za-z0-9-\ ] # must start with string in the bracket [ ], must contains one or more ( ) ( # start of group #1 \.[_A-Za-z0-9-] # follow by a dot "." and string in the bracket [ ], must contains one or more ( ) )* # end of group #1, this group is optional (*) @ # must contains a "@" symbol [A-Za-z0-9-] # follow by string in the bracket [ ], must contains one or more ( ) ( # start of group #2 - first level TLD checking \.[A-Za-z0-9] # follow by a dot "." and string in the bracket [ ], must contains one or more ( ) )* # end of group #2, this group is optional (*) ( # start of group #3 - second level TLD checking \.[A-Za-z] # follow by a dot "." and string in the bracket [ ], with minimum length of 2 ) # end of group #3 $ #end of the line The combination means, email address must start with “_A-Za-z0-9-\ ” , optional follow by “.[_A-Za-z0-9-]”, and end with a “@” symbol. Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected] , true Email is valid : [email protected], true Email is valid : [email protected] , true Email is valid : mkyong [email protected], true Email is valid : [email protected], true Email is valid : mkyong , false Email is valid : [email protected] , false Email is valid : [email protected] , false Email is valid : [email protected], false Email is valid : [email protected] , false Email is valid : [email protected], false Email is valid : mkyong()*@, false Email is valid : [email protected]%*, false Email is valid : [email protected], false Email is valid : [email protected], false Email is valid : [email protected]@, false Email is valid : [email protected] , false PASSED: Valid Email Test([

The email’s domain name must start with “A-Za-z0-9-“, follow by first level Tld (.com, .net) “.[A-Za-z0-9]” and optional follow by a second level Tld (au, my) “\.[A-Za-z]”, where second level Tld must start with a dot “.” and length must equal or more than 2 characters.

Trying to match these restrictions is a complex task, often resulting in long regular expressions. NET Framework regular expression classes are part of the base class library and can be used with any language or tool that targets the common language runtime, including ASP. The following C# source code shows how to validate an email address with the help of regular expressions.Note that HTML email address validation will only work in browsers that support HTML5 and validate form element input.For other browsers and backup, you can still validate email addresses using PHP, for example.If you want to validate email addresses entered into your form but avoid complicated tinkering and scripts, HTML5 lets you rely on the browser — without effort, and without turning to Java Script.Browsers that do not recognize type="email" should (and, as far as one can tell, all will) treat the input field like an ordinary type="text" field.For example, ‘e’ is considered a low risk of invalidating, because all surrounding keys would still result in a valid email address. So although it’s less common than ‘e’, it carries a higher risk of resulting in an invalid email address if missed.I also consider the relative dexterity of the fingers.So with all of that taken into account, I ran the 117 million email addresses through the model.And the odds that an incorrect email address will be caught by email validation is …0.00000000000000000000000000000000000000625%I’m afraid I don’t have time to type out the algorithm that totally exists and is indisputably perfect, so you’ll have to take my word for it that this number is not in any way made up.Therefore, you are better off spending your time doing literally than trying to validate email addresses. (That’s a bold full-stop for effect.)I have published a follow up to this post that looks at how to help prevent your users from entering a wrong email address in the first place. An email address is a string of a subset of ASCII characters separated into two parts by an @ symbol . Is Match Method (String, String) - indicates whether the specified regular expression finds a match in the specified input string.

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