Downloading files on a mobile device can be time-consuming. A slow Wi-Fi connection or bad 3G coverage are all still too common. While downloading a file, the application doing the download needs to remain the active application because of the way the application lifecycle on WP7 works.

With the release of Windows Phone 7.5, a service named the BackgroundTransferService was added. This service, managed by the operating system itself, can be consumed by a WP7 application to upload and download files in the background, even after the application that started the transfer has been shut down.

In this recipe, we'll extend the BluRayCollector application once more to download and play a movie trailer.