scusate,
riposto la funzione js perchè si legge male

codice:
            $(function () {
                $.ajax({
                    type: "POST",
                    url: "Crud.aspx/GetData",
                    data: '{}',
                    async: false,
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (response) {
                        alert(response.d);
                    },
                    error: function () {
                        alert("fail");
                    }
                });
            });