What is the most elegant code to validate that a string is a valid email address?
What about this?
bool IsValidEmail(string email)
{
var trimmedEmail = email.Trim();
if (trimmedEmail.EndsWith(".")) {
return false; // suggested by @TK-421
}
try {
var addr = new System.Net.Mail.MailAddress(email);
return addr.Address == trimmedEmail;
}
catch {
return false;
}
}
Per Stuart's comment, this compares the final address with the original string instead of always returning true. MailAddress tries to parse a string with spaces into "Display Name" and "Address" portions, so the original version was returning false positives.
To clarify, the question is asking whether a particular string is a valid representation of an e-mail address, not whether an e-mail address is a valid destination to send a message. For that, the only real way is to send a message to confirm.
Note that e-mail addresses are more forgiving than you might first assume. These are all perfectly valid forms:
For most use cases, a false "invalid" is much worse for your users and future proofing than a false "valid". Here's an article that used to be the accepted answer to this question (that answer has since been deleted). It has a lot more detail and some other ideas of how to solve the problem.
Providing sanity checks is still a good idea for user experience. Assuming the e-mail address is valid, you could look for known top-level domains, check the domain for an MX record, check for spelling errors from common domain names (gmail.cmo), etc. Then present a warning giving the user a chance to say "yes, my mail server really does allow 🌮🍳🎁 as an email address."
As for using exception handling for business logic, I agree that is a thing to be avoided. But this is one of those cases where the convenience and clarity may outweigh the dogma.
Besides, if you do anything else with the e-mail address, it's probably going to involve turning it to a MailAddress. Even if you don't use this exact function, you will probably want to use the same pattern. You can also check for specific kinds of failure by catching different exceptions: null, empty, or invalid format.
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