How do I use a custom validator in ASP.NET

<pre>asp:TableRow>
            <asp:TableCell>Email</asp:TableCell>
             <asp:TableCell>
                <asp:TextBox runat="server" ID="email"  CausesValidation="true"></asp:TextBox>
               <asp:RequiredFieldValidator runat="server" ID="emailvalidator" ControlToValidate="email"  ErrorMessage="Email required" style="color:red"></asp:RequiredFieldValidator>
               <asp:CustomValidator runat="server"  ControlToValidate="email" ErrorMessage="Valid Email required" ValidateEmptyText="True" ClientValidationFunction="validatemail" EnableClientScript="true" OnServerValidate="email_serverValidation"></asp:CustomValidator>
            </asp:TableCell>
        </asp:TableRow>

<pre>    <script type="text/javascript">
        function validatemail(sender,args)
        {
            debugger;
            var val = args.Value;
            var regex = /^[a-zA-Z0-9]{1-10}@[a-zA-Z]{1-10}.(com|org)$/;
            if(regex.test(val))
            {
                args.IsValid = true;
            }
        }
    </script>

protected void email_serverValidation(object sender, ServerValidateEventArgs e)
       {

           System.Text.RegularExpressions.Regex r = new System.Text.RegularExpressions.Regex("^([a-zA-Z0-9]+)@[a-zA-Z]{1-10}.(com|org)$");
           if (r.IsMatch(email.Text))
           {
               e.IsValid = true;
           }

       }