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

I am using the following regular expressions to validate the e-mail, but this also allows empty string , How can I change it? To stop this:

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

I am using an asp: RegularExpressionValidator my second option is to add on ASP: RequiredFieldValidator, but I'm curious if it's in my regular Expression Validator It is possible to check the spaces, so I do not have 2

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