Question

I have the following ASP.NET markup:

<asp:regularexpressionvalidator id="RegularExpressionValidator7"
            runat="server" 
            ControlToValidate="Email1" 
            ErrorMessage="Email not valid" 
            ValidationExpression="\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*">

As you can see, the validation expression is the one that Visual Web Developer gives as default. It has always worked great for me, until someone tried to enter this e-mail address:

[e-mail]

The validator says that the email is not valid, but it is. I verified at hotmail.com and you can create an e-mail address with a hyphen just before the @ symbol.

What must I change in the validation expression to accept this hyphen?

Answer 1

Add an optional hyphen (-?) before the @ in your regex.

ValidationExpresion="\w+([-+.]\w+)*-?@\w+([-.]\w+)*\.\w+([-.]\w+)*"
....................change.here....^^

Are you allowed a + just before the hyphen too? Then you’d add it in like

ValidationExpresion="\w+([-+.]\w+)*[-+]?@\w+([-.]\w+)*\.\w+([-.]\w+)*"
.....................change.here...^^^^^

and so on.