asp.net - Windows Phone 8 の「System.NotSupportedException」Web API

Question

WP8 アプリからローカルの asp.net Web API メソッドを呼び出して、例外を取得しています。

asyncResult.AsyncWaitHandle' がタイプ 'System.NotSupportedException' の例外をスローしました

誰でもこれを手伝ってもらえますか？

  public void GetProducts()
    {
        UriBuilder fullUri = new UriBuilder(baseUri + "productapi");
        fullUri.Query = "";

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(fullUri.Uri);
        request.Accept = "application/json";
        RequestUpdateState requestState = new RequestUpdateState();
        requestState.AsyncRequest = request;

        request.BeginGetResponse(new AsyncCallback(HandleProductsResponse),
            requestState);
    }

    private void HandleProductsResponse(IAsyncResult asyncResult)
    {
        // get the state information
        RequestUpdateState requestState = (RequestUpdateState)asyncResult.AsyncState;
        HttpWebRequest request = (HttpWebRequest)requestState.AsyncRequest;

        // end the async request
        requestState.AsyncResponse = (HttpWebResponse)request.EndGetResponse(asyncResult);

        Stream streamResult;        
        // get the stream containing the response from the async call
        streamResult = requestState.AsyncResponse.GetResponseStream();
        ObservableCollection<Product> productList = new ObservableCollection<Product>();

    }