private void btnCache_Click(object sender, RoutedEventArgs e)
        {
            btnCache.IsEnabled = false;
            var th = new Thread(() =>
            {
                WebImage.ClearCache();

                Dispatcher.Invoke(new Action(() =>
                {
                    loadCacheSize();
                    btnCache.IsEnabled = true;
                }));
            });

            th.Start();
        }