private void OnRequestFinished(MvxFastFileDownloadRequest request)
 {
     RunSyncOrAsyncWithLock(() =>
     {
         _currentRequests.Remove(request);
         if (_queuedRequests.Any())
         {
             StartNextQueuedItem();
         }
     });
 }
        public void RequestDownload(string url, string downloadPath, Action success, Action <Exception> error)
        {
            var request = new MvxFastFileDownloadRequest(url, downloadPath);

            request.DownloadComplete += (sender, args) =>
            {
                OnRequestFinished(request);
                success();
            };
            request.DownloadFailed += (sender, args) =>
            {
                OnRequestFinished(request);
                error(args.Value);
            };

            RunSyncOrAsyncWithLock(() =>
            {
                _queuedRequests.Enqueue(request);
                if (_currentRequests.Count < _maxConcurrentDownloads)
                {
                    StartNextQueuedItem();
                }
            });
        }