Regular expression to validate comma separated email addresses?

Question

I need to validate email addresses which can be single or several comma-separated ones.

Before I was using in a regular expression validator an expression like:

string exp = @"((\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*)*([,])*)*";

and it was validating multiple or one single email address.

But same expression is not valdiating in C#? It says valid to invalid addresses as well.

Please correct me or suggest me an expression to validate email addresse(s).

Answer 1

Please give more details. Which addresses are matched as valid, but should be invalid? How do you call the regex (your c# code)?

A point I see is that you are missing anchors.

 ^((\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*)*([,])*)*$

^ matches the start of the string

$ matches the end of the string

If you don't use them your pattern will match as soon as it found a valid sub string.

Answer 2

i dont know C# i can give an idea split by ',' and validate each seperator..... its simple

Answer 3

Without knowing how you're doing the validation, it's hard to tell why C# is validating some strings that the validator had rejected. Most probably it's because the validator is looking at the entire string, and you're using Regex.IsMatch() in C# which would also accept the match if a substring matches. To work around that, add \A to the start and \Z to the end of your regex. In your case, the entire regex is optional (enclosed by (...)*) so it also matches the empty string - do you want to allow that?

Then again, you might want to reconsider the regex approach entirely - no sane regex can validate e-mail addresses correctly (and you'll still pass addresses that just look valid but don't have an actual account associated with them).