如何将windows8应用程序c与phpapi连接

我在这段代码中尝试连接到windows8应用程序的php基api服务器。但是，我不知道如果我尝试调试它，url是正确的，并且变量是设置好的，所以我没有得到任何结果。我是windows8应用程序和c#的新手，经过几次研究，这就是连接到api服务器的样子请帮忙

private void Button_Click(object sender, RoutedEventArgs e)
        {
            var username="lucy";
            var password="lucy";
            var request = HttpWebRequest.Create("http://myURL/login.php?username="+username+"&password="+password) as HttpWebRequest;
            request.Method = "POST";
            request.ContentType = "text/json";
            request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
        }
private void GetRequestStreamCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
        // End the stream request operation
        Stream postStream = request.EndGetRequestStream(asynchronousResult);

        // Create the post data
        string postData = JsonConvert.SerializeObject(postStream).ToString();
        MessageDialog msgDialog1 = new MessageDialog(postData, "bayyanit");
      msgDialog1.ShowAsync();
        Debug.WriteLine(postData);
        byte[] byteArray = Encoding.UTF8.GetBytes(postData);

        postStream.Write(byteArray, 0, byteArray.Length);
      //  postStream.Close();
        //Start the web request
        try
        {
            request.BeginGetResponse(new AsyncCallback(GetResponceStreamCallback), request);
        }
    catch(Exception ex)
        {
            MessageDialog msgDialog = new MessageDialog(ex.ToString(), "bayyanit");
            msgDialog.ShowAsync();
        }
    }
    void GetResponceStreamCallback(IAsyncResult callbackResult)
    {
        HttpWebRequest request = (HttpWebRequest)callbackResult.AsyncState;
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(callbackResult);
        using (StreamReader httpWebStreamReader = new StreamReader(response.GetResponseStream()))
        {
            string result = httpWebStreamReader.ReadToEnd();
            MessageDialog msgDialog = new MessageDialog(result, "bayyanit");
            msgDialog.ShowAsync();
        }
    }