How to know if current culture in ASP.Net Webforms app is based on English alphabets

I have a regular expression validator in an ASP.Net Webforms app that makes sure the input in a textbox is a combination of these characters alphabets, digits, period, hyphen and single quote as in code below. Since this ASP.Net is multi-lingual i.e. both English and non-English cultures are allowed, the regex validator will need to b disabled when its being accessed from a non-English culture.

Question

Is the code-behind mentioned below going to satisfy this requirement of disabling the regex validator when being accessed from a non-English culture, Or is the code lacking something?

Regex Validator

<asp:RegularExpressionValidator 
ID="revProdName" runat="server" 
ErrorMessage="RegularExpressionValidator" ControlToValidate="ctxtProductName" 
ValidationExpression="^[(a-z)(A-Z) .'-(0-9)]+$"></asp:RegularExpressionValidator>

Code-behind of page

 If System.Globalization.CultureInfo.CurrentUICulture.DisplayName.StartsWith("en-") Then
            revProdName.Enabled = True
        Else
            revProdName.Enabled = False
        End If