javascript 控制是否要啟用驗證控制項

javascript:
        $(document).ready(function () {
            if ($('#txt2').val() == '') {
                ValidatorEnable($('#rfvtxt')[0], true);

            } else
                ValidatorEnable($('#rfvtxt')[0], false);
            $('#txt2').change(function () {
                if ($('#txt2').val() =='') {
                    ValidatorEnable($('#rfvtxt')[0], true);

                } else
                    ValidatorEnable($('#rfvtxt')[0], false);
            });
        });
        function validatePage() {
            var flag = Page_ClientValidate("aaa");
            return flag;
        }
html:


    <asp:RequiredFieldValidator runat="server" ID="rfvtxt" ControlToValidate="TXT" ErrorMessage="*"   ValidationGroup="aaa"  Enabled="false"></asp:RequiredFieldValidator>
        <asp:Button runat="server" OnClick="Unnamed_Click"   OnClientClick="javascript:return validatePage();"/>


cs.
 Page.Validate();
        if (!Page.IsValid)
        {
            return;
        }


寫成function做法
http://techbrij.com/client-side-validation-using-asp-net-validator-controls-from-javascript