private async Task RunDownloadsAsync()
{
// Create a downloader and associate all its downloads with the transfer group used for
// this scenario.
BackgroundDownloader downloader = new BackgroundDownloader();
downloader.TransferGroup = reorderGroup;
// Validating the URI is required since it was received from an untrusted source (user
// input).
// The URI is validated by calling Uri.TryCreate() that will return 'false' for strings
// that are not valid URIs.
// Note that when enabling the text box users may provide URIs to machines on the
// intranet that require the "Private Networks (Client and Server)" capability.
string remoteAddress = remoteAddressField.Text.Trim();
Uri tmpUri;
if (!Uri.TryCreate(remoteAddress, UriKind.Absolute, out tmpUri))
{
rootPage.NotifyUser("Invalid URI.", NotifyType.ErrorMessage);
return;
}
string fileName = fileNameField.Text.Trim();
if (string.IsNullOrWhiteSpace(fileName))
{
rootPage.NotifyUser("A local file name is required.", NotifyType.ErrorMessage);
return;
}
// Try to create some downloads.
DownloadOperation[] downloads = new DownloadOperation[NumDownloads];
try
{
for (int i = 0; i < NumDownloads; i++)
{
string currRemoteAddress = $"{remoteAddress}?id={i}";
string currFileName = $"{i}.{fileName}";
downloads[i] = await CreateDownload(downloader, currRemoteAddress, currFileName);
}
}
catch (FileNotFoundException ex)
{
rootPage.NotifyUser($"Error while creating file: {ex.Message}", NotifyType.ErrorMessage);
return;
}
// Once all downloads have been created, start them.
Task[] downloadTasks = new Task[downloads.Length];
downloadCollection.Clear();
for (int i = 0; i < downloads.Length; i++)
{
DownloadOperationItem item = new DownloadOperationItem(downloads[i]);
downloadTasks[i] = DownloadAsync(item);
downloadCollection.Add(item);
}
await Task.WhenAll(downloadTasks);
}
private async Task DownloadAsync(DownloadOperationItem item)
{
Progress <DownloadOperation> progressCallback = new Progress <DownloadOperation>(
(operation) => DownloadProgress(item));
try
{
await item.download.StartAsync().AsTask(progressCallback);
item.stateText = item.download.Progress.Status.ToString();
rootPage.NotifyUser(
$"Downloading {item.download.ResultFile.Name} completed.",
NotifyType.StatusMessage);
}
catch (Exception ex)
{
// Ignore canceled downloads since they are not displayed.
if (item.download.Progress.Status != BackgroundTransferStatus.Canceled)
{
// Ensure that we reach 100% even for errors.
item.percentComplete = 100;
item.stateText = item.download.Progress.Status.ToString();
if (!IsWebException("Execution error", ex, item.download))
{
throw;
}
}
}
}
private void MakeCurrent_Click(object sender, RoutedEventArgs e)
{
Button button = sender as Button;
DownloadOperationItem item = button.DataContext as DownloadOperationItem;
// Make the selected operation current.
item.download.MakeCurrentInTransferGroup();
}
private void DownloadProgress(DownloadOperationItem item)
{
BackgroundDownloadProgress currentProgress = item.download.Progress;
BackgroundTransferStatus status = currentProgress.Status;
int percentComplete = 0;
if (currentProgress.TotalBytesToReceive > 0)
{
percentComplete = (int)((currentProgress.BytesReceived * 100) / currentProgress.TotalBytesToReceive);
}
var ignore = this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
item.stateText = status.ToString();
item.percentComplete = percentComplete;
});
}
