<asp:CustomValidator ID="custvalBirthCenters" runat="server" ControlToValidate="rbBirthCenters" ValidationGroup="DoulaProfile" OnServerValidate="ValidateBirthCenters" ErrorMessage="Please indicate whether you attend births at birth centers." Display="Dynamic" Text="*" CssClass="validation" Enabled="true" ValidateEmptyText="true" ></asp:CustomValidator>