webclient I/O error while sending multiple request to API - windows-phone-7

Question

I want to make Twitter Sentiment Analysis Windows Phone Application.
the application works by retrieving all the related tweets based on what query terms that users entered. for example, if I enter "Windows Phone" in input search box, the results will show all the tweet that contains "windows phone" terms.
here's the code (that I get from Arik Poznanski's Blog)
/// <summary>
/// Searches the specified search text.
/// </summary>
/// <param name="searchText">The search text.</param>
/// <param name="onSearchCompleted">The on search completed.</param>
/// <param name="onError">The on error.</param>
public static void Search(string searchText, Action<IEnumerable<Twit>> onSearchCompleted = null, Action<Exception> onError = null, Action onFinally = null)
{
WebClient webClient = new WebClient();
// register on download complete event
webClient.OpenReadCompleted += delegate(object sender, OpenReadCompletedEventArgs e)
{
try
{
// report error
if (e.Error != null)
{
if (onError != null)
{
onError(e.Error);
}
return;
}
// convert json result to model
Stream stream = e.Result;
DataContractJsonSerializer dataContractJsonSerializer = new DataContractJsonSerializer(typeof(TwitterResults));
TwitterResults twitterResults = (TwitterResults)dataContractJsonSerializer.ReadObject(stream);
App thisApp = Application.Current as App;
thisApp.klasifikasi = new Klasifikasi();
foreach (Twit Tweet in twitterResults.results)
{
try
{
thisApp.klasifikasi.UploadData(Tweet); //requesting
break;
}
finally
{
// notify finally callback
if (onFinally != null)
{
onFinally();
}
}
}
//thisApp.klasifikasi.UploadDatas(twitterResults.results);
//thisApp.PositiveTweetModel = new PositiveTweetModel("Positive", twitterResults.results);
// notify completed callback
if (onSearchCompleted != null)
{
onSearchCompleted(twitterResults.results);
/// Divide the list here
}
}
finally
{
// notify finally callback
if (onFinally != null)
{
onFinally();
}
}
};
string encodedSearchText = HttpUtility.UrlEncode(searchText);
webClient.OpenReadAsync(new Uri(string.Format(TwitterSearchQuery, encodedSearchText)));
}
and to call the method
TwitterService.Search(
text,
(items) => { PositiveList.ItemsSource = items; },
(exception) => { MessageBox.Show(exception.Message); },
null
);
to upload POST Data into the API
public void UploadData(Twit tweetPerSend)
{
if (NetworkInterface.GetIsNetworkAvailable())
{
chatterbox.Headers[HttpRequestHeader.ContentType] = "application/x-www- form-urlencoded";
chatterbox.Headers["X-Mashape-Authorization"] = "MXBxYmptdjhlbzVnanJnYndicXNpN2NwdWlvMWE1OjA0YTljMWJjMDg4MzVkYWY2YmIzMzczZWFkNDlmYWRkNDYzNGU5NmI=";
var Uri = new Uri("https://chatterboxco-sentiment-analysis-for-social-media---nokia.p.mashape.com/sentiment/current/classify_text/");
StringBuilder postData = new StringBuilder();
postData.AppendFormat("{0}={1}", "lang", HttpUtility.UrlEncode("en"));
postData.AppendFormat("&{0}={1}", "text", HttpUtility.UrlEncode(tweetPerSend.DecodedText));
postData.AppendFormat("&{0}={1}", "exclude", HttpUtility.UrlEncode("is")); // disesuaikan
postData.AppendFormat("&{0}={1}", "detectlang", HttpUtility.UrlEncode("0"));
chatterbox.UploadStringAsync(Uri, "POST", postData.ToString());
chatterbox.UploadStringCompleted += new UploadStringCompletedEventHandler(chatterbox_UploadStringCompleted);
}
}
void chatterbox_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
{
var chatterbox = sender as WebClient;
chatterbox.UploadStringCompleted -= chatterbox_UploadStringCompleted;
string response = string.Empty;
if (!e.Cancelled)
{
response = HttpUtility.UrlDecode(e.Result);
nilaiKlasifikasi = ParsingHasil(response);
MessageBox.Show(nilaiKlasifikasi.ToString()); //just testing
//textBlock1.Text = response;
}
}
private double ParsingHasil(String response)
{
var result = Regex.Match(#response, #"(?<=""value"": )(-?\d+(\.\d+)?)(?=,|$)");
Debug.WriteLine(result);
double hasil = Convert.ToDouble(result.ToString());
//return Convert.ToInt32(result);
return hasil;
}
However, there isn't only 1 tweet to retrieve, there'll be many tweets, so the main problem is, after I retrieve all the tweet and request the result to the API, I get this error "WebClient does not support concurrent I/O operations"
Does anyone know how to solve this problem?
any help would be appreciated

Answer 1

You'll have to execute UploadStringAsync synchronously one at a time. (i.e. chain execution of the next UploadStringAsync in the UploadStringCompleted handler.
Or, create a new WebClient for each UploadStringAsync.