c# - Windows Phone 8.1 货币转换器 Json

Question

我有一个学校项目。我必须做一个货币转换器，我被卡住了。我在Code Project 网站上找到了一些东西，但我是新手，我真的不知道如何在我的项目中实现它。

我尝试了类似`

public sealed partial class MainPage : Page
{
    public MainPage()
    {

        this.InitializeComponent();

        this.NavigationCacheMode = NavigationCacheMode.Required;

    }


    protected override void OnNavigatedTo(NavigationEventArgs e)
    {


    }
    class WebClient
    {
        internal string DownloadString(string url)
        {

            throw new NotImplementedException();

            url = "https://openexchangerates.org/api/latest.json?app_id=ae11142304694b10a1dbf2d25933a333";
            var currencyRates = _download_serialized_json_data<App9.CurrencyRates>(url);
        }
    }
    public static T _download_serialized_json_data<T>(string url) where T : new()
    {
        var w = new WebClient();
        {
            //using (var w = new WebClient()) {
            var json_data = string.Empty;
            // attempt to download JSON data as a string
            try
            {
                json_data = w.DownloadString(url);
            }
            catch (Exception) { }
            // if string with JSON data is not empty, deserialize it to class and return its instance 
            return !string.IsNullOrEmpty(json_data) ? JsonConvert.DeserializeObject<T>(json_data) : new T();
        }
    }

    private void comboBoxTo_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {

    }

    private void convertButton_Click(object sender, RoutedEventArgs e)
    {
        if (amountTb.Text == string.Empty)
        {
            afisareTb.Text = "Scrieti o valoare";
        }
        else
        {

            var currencyRates = _download_serialized_json_data<CurrencyRates>("https://openexchangerates.org/api/latest.json?app_id=YOUR_APP_ID "); 
        }

    }
}

`

我没有任何错误，只是当我从我的应用程序中按下转换器按钮时，没有任何反应。