RegEx - Only one valid email

I know it's my fault and it is not complicated but I cannot find the answer by myself so I beg you to help me build this RegEx.

I'm trying to avoid users to enter more than one email address by line, so I'd like to limit the "@" occurrences to only 1 and also check there are not commas (,)....

Here's a simplified version of the RegEx I'm already using to check the 开发者_如何学编程input....

\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b

How could I introduced a section to check there are not (@,) on the last part ?

Thanks in advance

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Instead of using a regex, you could split the string at the @, and count how many elements the output array has.

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Try just to add an ^ and one $

^\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b$

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This is what I am currently using. A quick test limited it to a single valid email for me.

@"^(?!.*\.\.)[a-zA-Z0-9\w\._%&!'*=?^+-]*@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]*\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$"