Email address validation in C# MVC 4 application: with or without using Regex [duplicate]

Question

This question already has answers here:

Email address validation using ASP.NET MVC data type attributes (11 answers)

Closed 7 years ago.

I have an MVC 4 web application and I need to enter and validate some email addresses, without sending an email to the user's email address.

Currently I am using basic regex email validation with this pattern:

[RegularExpression(@"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z",
        ErrorMessage = "Please enter correct email address")]

Although this is validating email addresses, it passes 1@1.1 as a valid email address. For the moment I have a validation that requires symbols @ symbols . symbols where the symbols can be numeric/alphabetic and ._- .

I need more standard email validation for my MVC 4 application. How do I do that?

Answer 1

You need a regular expression for this. Look here. If you are using .net Framework4.5 then you can also use this. As it is built in .net Framework 4.5. Example

[EmailAddress(ErrorMessage = "Invalid Email Address")]
public string Email { get; set; }

Answer 2

Expanding on Ehsan's Answer....

If you are using .Net framework 4.5 then you can have a simple method to verify email address using EmailAddressAttribute Class in code.

private static bool IsValidEmailAddress(string emailAddress)
{
    return new System.ComponentModel.DataAnnotations
                        .EmailAddressAttribute()
                        .IsValid(emailAddress);
}

If you are considering REGEX to verify email address then read:

I Knew How To Validate An Email Address Until I Read The RFC By Phil Haack

Answer 3

Regex:

[RegularExpression(@"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$", ErrorMessage = "Please enter a valid e-mail adress")]

Or you can use just:

    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }

Answer 4

Why not just use the EmailAttribute?

[Email(ErrorMessage = "Bad email")]
public string Email { get; set; }

Answer 5

Don't.

Use a regex for a quick sanity check, something like .@.., but almost all langauges / frameworks have better methods for checking an e-mail address. Use that.

It is possible to validate an e-mail address with a regex, but it is a long regex. Very long.
And in the end you will be none the wiser. You'll only know that the format is valid, but you still don't know if it's an active e-mail address. The only way to find out, is by sending a confirmation e-mail.

Answer 6

It is surprising the question of validating an email address continually comes up on SO!

You can find one often-mentioned practical solution here: How to Find or Validate an Email Address.

Excerpt:

The virtue of my regular expression above is that it matches 99% of the email addresses in use today. All the email address it matches can be handled by 99% of all email software out there. If you're looking for a quick solution, you only need to read the next paragraph. If you want to know all the trade-offs and get plenty of alternatives to choose from, read on.

See this answer on SO for a discussion of the merits of the article at the above link. In particular, the comment dated 2012-04-17 reads:

To all the complainers: after 3 hours experimenting all the solutions offered in this gigantic discussion, this is THE ONLY good java regex solution I can find. None of the rfc5322 stuff works on java regex.