In che modo inserisco la mia classe di aggiornamento e gestisco la richiesta / risposta dalla richiesta web HTTP?

Non so come organizzare il mio codice. Proprio ora ho scaricato tutto in MainPage per il test. Ma qual è il modo corretto per gestire il recupero dei dati dal servizio web REST in Windows Phone 8? Ho più pagine che devono utilizzare i dati che vengono restituiti.

    /// <summary>
/// State information for our BeginGetResponse async call
/// </summary>
public class UpdateState
{
    public HttpWebRequest AsyncRequest { get; set; }
    public HttpWebResponse AsyncResponse { get; set; }
}


public partial class MainPage : PhoneApplicationPage
{
    // Constructor
    public MainPage()
    {
        InitializeComponent();

        // Sample code to localize the ApplicationBar
        //BuildLocalizedApplicationBar();
    }

    private async void test()
    {

        var handler = new HttpClientHandler();
        if (handler.SupportsAutomaticDecompression)
        {
            handler.AutomaticDecompression = DecompressionMethods.GZip |
                                             DecompressionMethods.Deflate;
        }

        // form the URI
        UriBuilder fullUri = new UriBuilder("http://test/GetData?");
        fullUri.Query = "format=xml&param=test&dateFrom=20071225&dateTo=20080101";

        var httpClient = new HttpClient(handler);
        var str = await httpClient.GetStringAsync(fullUri.Uri);
        string test = "";
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {


        test();



        // form the URI
        UriBuilder fullUri = new UriBuilder("http://test/GetData?");
        fullUri.Query = "format=xml&param=test&dateFrom=20140124&dateTo=201425 ";

        // initialize a new WebRequest
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(fullUri.Uri);

        // set up the state object for the async request
        UpdateState state = new UpdateState();
        state.AsyncRequest = request;

        // start the asynchronous request
        request.BeginGetResponse(new AsyncCallback(HandleResponse),
            state);
    }

    /// <summary>
    /// Handle the information returned from the async request
    /// </summary>
    /// <param name="asyncResult"></param>
    private void HandleResponse(IAsyncResult asyncResult)
    {
        // get the state information
        UpdateState forecastState = (UpdateState)asyncResult.AsyncState;
        HttpWebRequest forecastRequest = (HttpWebRequest)forecastState.AsyncRequest;

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

        Stream streamResult;

        string newCredit = "";
        string newCityName = "";
        int newHeight = 0;

        string XMLresult = string.Empty;

        try
        {

            // get the stream containing the response from the async call
            string type = forecastState.AsyncResponse.ContentType; 
            streamResult = forecastState.AsyncResponse.GetResponseStream();

            XMLresult = getXMLData(streamResult);

            // load the XML
            XElement xmlData = XElement.Parse(XMLresult);

            string t = "";

        }
        catch (FormatException)
        {
            // there was some kind of error processing the response from the web
            // additional error handling would normally be added here
            return;
        }

    }