Post Json字符串到Web Api Windows Store 8.1

与webClient弃用和SharpRest不工作的Windows 8.1我需要传递我的json字符串到web api

字符串js = @"{"用户名":"jerin","标识":"一"}]";

var baseAddress = " http://epub3.in/sample/android%20webservice/webservice/insertuser.php/",

        HttpClient httpClient = new HttpClient();
         HttpClient httpClient = new HttpClient();
        httpClient.BaseAddress = new Uri(baseAddress);
        httpClient.DefaultRequestHeaders.Accept.Clear();
        httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        try
        {
            HttpResponseMessage response =  httpClient.PostAsync("",
                new StringContent(
                    js,
                    Encoding.UTF8,
                    "application/json")).Result;
              string sd = response.IsSuccessStatusCode.ToString();}

现在baseaddress是一个字符串，它有url地址。但即使我得到IsSuccessStatusCode为真json没有被输入。
我应该看到输入的结果在这个链接
Android团队发布的参数值为

usersJSON =[{"用户名":"jerin"、"用户名":"3"}]

根据@Jon的回答，我编辑了我的代码，而不是System.Net.Http，我现在使用Windows.Web.http，但它仍然没有上传

        Windows.Web.Http.HttpClient httpClient = new Windows.Web.Http.HttpClient();
        Windows.Web.Http.HttpRequestMessage msg = new Windows.Web.Http.HttpRequestMessage(new Windows.Web.Http.HttpMethod("POST"), new Uri(baseAddress));
        msg.Content = new HttpStringContent((js));
        msg.Content.Headers.ContentType = new HttpMediaTypeHeaderValue("application/json");
        Windows.Web.Http.HttpResponseMessage response = await httpClient.SendRequestAsync(msg).AsTask();

            HttpClient httpClient = new HttpClient();
            HttpRequestMessage msg = new HttpRequestMessage(new HttpMethod("POST"), new Uri(baseAddress));
            msg.Content = new HttpStringContent(js);
            msg.Content.Headers.ContentType = new HttpMediaTypeHeaderValue("application/json");
            HttpResponseMessage response = await _httpClient.SendRequestAsync(msg).AsTask();