public override void DidCompleteWithError(Foundation.NSUrlSession session, Foundation.NSUrlSessionTask task, Foundation.NSError error)
 {
     // Add a breakpoint here if you encounter any errors.
 }
        public override void DidFinishEventsForBackgroundSession(Foundation.NSUrlSession session)
        {
            // If you want to notify the users, that all files are downloaded, do it here - before the base-method is called.

            base.DidFinishEventsForBackgroundSession(session);
        }