使用C#在Windows 8 metro应用程序上发送POST请求

我试着用C#发出一个POST请求很长一段时间，但它始终不起作用
来自服务器的statusCode是200，所以它似乎可以工作，但我得到的响应是"AccessDenied"。HTTP标头似乎是错误
在JS上发出的POST请求效果很好，但在C#上没有
以下是请求：

string resourceAddress = " ... ";
try
{
     HttpClient httpClient = new HttpClient();  
     var content = new List<KeyValuePair <string,string>>
     {
       new KeyValuePair<string,string>(" ... "," ... "),
         ...
     };
     HttpResponseMessage response = await httpClient.PostAsync(resourceAddress, new FormUrlEncodedContent(content));
     response.EnsureSuccessStatusCode();
     var responseString = await response.Content.ReadAsStringAsync(); 
}
catch (HttpRequestException hre)   
{
      Debug.WriteLine(hre.ToString());
}
catch (Exception ex)   
{
      Debug.WriteLine(ex.ToString());
}

我错过什么了吗
带有C#请求的Windows8是否修改或添加了一些内容到标题中？

在安卓系统上，我使用以下代码：

HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(urlWebSiteHTTPRequest);
try
{           
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
    nameValuePairs.add(new BasicNameValuePair("... ","... "));
    ....
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
    response = httpclient.execute(httppost);
    entity = response.getEntity();
    responseText = EntityUtils.toString(entity);
}   
catch (ClientProtocolException e) 
{
    // TODO Auto-generated catch block
} 
catch (IOException e) 
{
    // TODO Auto-generated catch block
}