[WebMethod]
    public static string GetCustomersByCountry(string country, string city)
    {
            return "";
    }

function GetCustomersByCountry() {
            var data = {
                "country": $('#Country').val()
            };
            $.ajax({
                type: "POST",
                url: "Customers2.aspx/GetCustomersByCountry",
                data: JSON.stringify(data),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    displayCustomers(response.d);
                },
                error: function (xhr, ajaxOptions, thrownError) {
                    alert(thrownError);
                }
            });
        }