How do I get the following regular expression to not allow blank e-mails?

I am using the following regular expression to validate e-mails, but it allows empty strings as well, how can I 开发者_开发百科change it to prevent it:

^[\w\.\-]+@[a-zA-Z0-9\-]+(\.[a-zA-Z0-9\-]{1,})*(\.[a-zA-Z]{2,3}){1,2}$

I am using an asp:RegularExpressionValidator. My other option is to add on a asp:RequiredFieldValidator, but I am curious if this is possible to check for blanks in my RegularExpressionValidator, so I don't have to have 2

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see http://www.regular-expressions.info/email.html

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That expression does not match empty strings. The expression starts with ^[\w\.\-]+ this translates to "The string must start with a word character, period or slash. There can be more than one of these." There must be something else wrong or you copied the expression incorrectly.

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This RegEx validates if a given string is in a valid email-format or not:

/^[a-zA-Z0-9\_\-\.]+\@([a-zA-Z0-9\-]+\.)+[a-zA-Z0-9]{2,4}$/