Windows Store App and Downloading & Progress Bar (C#)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Windows.Devices.Geolocation;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

using System.Net.Http;
using Windows.Networking.BackgroundTransfer;
using Windows.Storage;
using System.Threading.Tasks;



// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238

namespace WindowsStoreApps
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    /// 

    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private DownloadOperation activeDownload; 

        private async void btnDownload_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                Uri source = new Uri(this.txtURL.Text);
                string destination = "myZip.zip";

                Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
                StorageFile destinationFile = await localFolder.CreateFileAsync(destination, CreationCollisionOption.ReplaceExisting);

                BackgroundDownloader downloader = new BackgroundDownloader();
                DownloadOperation download = downloader.CreateDownload(source, destinationFile);

                await HandleDownloadAsync(download);
            }
            catch (Exception ex)
            {
                //LogException("Download Error", ex);
            }
        }

        private void ProgressCallback(DownloadOperation obj)
        {
            double progress
                = ((double)obj.Progress.BytesReceived / obj.Progress.TotalBytesToReceive);
            DownloadProgress.Value = progress * 100;
            if (progress >= 1.0)
            {
                activeDownload = null;
            }
        }

        private async Task HandleDownloadAsync(DownloadOperation downloadOperation)
        {
            activeDownload = downloadOperation;
            var progress = new Progress<DownloadOperation>(ProgressCallback);
            await downloadOperation.StartAsync().AsTask(progress);
        }
       
    }
}