用于电子邮件地址验证的正则表达式

Question

I am trying to validate email addresses. Currently I'm using the following regex to validate email addresses which works perfectly fine. But I now want to tweek it and allow only min 2 and max 40 characters for the domain-part of the email address ie after the @ symbol. I tried setting the range but I guess it wont work like this. Where am I going wrong?

The Regex:

^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,})$

Answer 1

Validating email addresses is non-trivial, and your regex as it is rejects perfectly good email addresses such as test+1234@localhost . If you need to do it yourself, have a look at RFC 822 §6 .

However, in C#, there is a class MailAddress with a constructor accepting a string argument. You can attempt to construct a MailAddress addr = new MailAddress(emailString) , and see whether it throws a FormatException . As a benefit, the MailAddress object has many useful methods for working with email addresses.

EDIT: My apologies, I missed that you were trying to limit the host length. If you create the MailAddress as above, then addr.Host will contain the hostname part, and you can check its length.