using (var hc = new HttpClient())
{
    var codes = new List<string();	
    hc.BaseAddress = new Uri(serviceUrl);
    hc.DefaultRequestHeaders.Accept.Clear();
    hc.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    HttpResponseMessage response = hc.PostAsJsonAsync("", codes).Result;
}