问在JSON中获取webservice的400状态时返回false

EN

private void loginAction(object sender, TappedRoutedEventArgs e)
{
    Webservice webservice = new Webservice();
    webservice.getUser(txtLogin.Text, txtPass.Text);
}

public void getUser(String user, String password)
{
    String strUrl = String.Format("http://*******/nl/webservice/abc123/members/login?email={0}&password={1}",user,password);

    startWebRequest(strUrl, loginCallback);
}

private async void loginCallback(IAsyncResult asyncResult)
{
    try
    {
        ReceiveContext received = GetReceiveContextFromAsyncResult(asyncResult, "User");

        if (received != null && received.Status == 200)
        {
            await UserDataSource.AddUser(received.Data);
        }
        else
        {

            throw new Exception("failedddd");
        }
    }
    catch (Exception e)
    {

    }   
}

#region HELPERS
private void startWebRequest(string url, AsyncCallback callback)
{
    // HttpWebRequest.RegisterPrefix("http://",WebRequestCreator.ClientHttp);
    HttpWebRequest httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));

    // start the stream immediately
    httpWebRequest.AllowReadStreamBuffering = false;

    // asynchronously get a response
    httpWebRequest.BeginGetResponse(callback, httpWebRequest);
}

private ReceiveContext GetReceiveContextFromAsyncResult(IAsyncResult asyncResult, string context)
{
    // Request afleiding van de AsyncState uit het ontvangen AsyncResult
    HttpWebRequest httpWebRequest = (HttpWebRequest)asyncResult.AsyncState;
    HttpWebResponse httpWebResponse = null;

    try
    {
        // Response afleiden uit de Resuest via de methode EndGetResponse();
        httpWebResponse = (HttpWebResponse)httpWebRequest.EndGetResponse(asyncResult);

        string responseString;
        // using == IDisposable (automatische GC)
        using (StreamReader readStream = new StreamReader(httpWebResponse.GetResponseStream()))
        { //Stream van de response gebruiken om een readstream te maken.
            responseString = readStream.ReadToEnd();
        }
        // Release the HttpWebResponse
        //httpWebResponse.Dispose();

        return new ReceiveContext(int.Parse(responseString.Substring(10, 3)), responseString);
    }
    catch (WebException wex)
    {
        Debug.WriteLine(String.Format("{0} kon niet opgehaald worden: {1}", context, wex.Message));
    }
    catch (JsonReaderException jrex)
    {
        Debug.WriteLine(String.Format("{0} opgehaald van server, maar de json kon niet geparsed worden: {1}", context, jrex.Message));
    }
    catch (FormatException fex)
    {
        Debug.WriteLine(String.Format("{0} opgehaald van server, maar de gegevens kloppen niet: {1}", context, fex.Message));
    }
    catch (ArgumentOutOfRangeException arex)
    {
        Debug.WriteLine(String.Format("{0} opgehaald van server, maar de context is leeg: {1}", context, arex.Message));
    }

    return null;
}
public sealed class ReceiveContext
{
    public ReceiveContext(int status, string data)
    {
        this.Status = status;
        this.Data = data;
    }

    public int Status { get; private set; }

    public string Data { get; private set; }
}
#endregion