namespace ConsoleApp1
{
class Program
{
static async Task Main(string[] args)
{
var appKey = "{app}";
var appSec = "{sec}";
var jsonStr = "{\"billCode\":\"73100059800035\"}";
using (HttpClient client = new HttpClient())
{
using (var content = new StringContent(jsonStr, Encoding.UTF8, "application/json"))
{
content.Headers.Add("x-appKey", appKey);