Regex for two consecutive dot email domain failure

Question

I am trying to verify the domain part of an email message, and I want to verify that there are no two consecutive points in the domain, that is, the following are not valid.

• joe @ ms..com
• joe @ ms.com..uk
• joe @ .. ms.com
• [e-mail]..

I have a regex to find it

@+\.{2}|@.+\.{2} 

but I use the Regex attribute in .NET and want to build a valid regular expression (i.e. a single number), and not the one that fails

I thought the ^ symbol means

all that is NOT an expression

so I thought ^(@+\.{2}|@.+\.{2}) would work, but it doesn’t support the .NET Framework EmailAddress Attribute - it stops joe@ms..com but does not stop [e-mail]..au

Answer 1

You can use negative lookup before your regex:

 @(?!.*?\.\.)[^@]+$ 

That will not coincide if there are 2 consecutive points in the domain somewhere in the domain.

[^@] will match 1 or more characters that are not @

RegEx Demo