how to call extraction function in background transfer download

Question

hi

    I have used background download transfer to download zip files,i have called zipextraction function

 function DownloadOperation() {
        var download = null;
        var promise = null;

        this.start = function (uri, destFolder, fileName, priority, requestUnconstrainedDownload) {
            var ext = fileName.substr(fileName.lastIndexOf('.'));
            if (ext.localeCompare(".zip") != 0) {
                displayError("Invalid file type. Please make sure the file type is zip.", NotifyType.ErrorMessage);
                return;
            }

            // Asynchronously create the file in the pictures folder.
            destFolder.createFileAsync(fileName, Windows.Storage.CreationCollisionOption.generateUniqueName).done(function (localFile) {
                var downloader = new Windows.Networking.BackgroundTransfer.BackgroundDownloader();

                // Create a new download operation.
                download = downloader.createDownload(uri, localFile);

                Log("Downloading " + uri.absoluteUri.toString() + "to " + destFolder.name + "with " + priority + " priority, " + download.guid);
                download.priority = priority;

                // In this sample, we do not show how to request unconstrained download.
                // For more information about background transfer, please refer to the SDK Background transfer sample:
                // http://code.msdn.microsoft.com/windowsapps/Background-Transfer-Sample-d7833f61
                if (!requestUnconstrainedDownload) {
                    // Start the download and persist the promise to be able to cancel the download.
                    promise = download.startAsync().then(complete, error, progress);

                    promise.done(function () {
                        if (download.progress.status === Windows.Networking.BackgroundTransfer.BackgroundTransferStatus.canceled) {
                            LogStatus("Canceled: " + download.Guid, NotifyType.StatusMessage);
                            return;
                        }
//zip extraction
                        var zipFileName = fileName.substr(0, fileName.lastIndexOf('.'));
                        destFolder.createFolderAsync(zipFileName, Windows.Storage.CreationCollisionOption.generateUniqueName).done(function (unzipFolder) {
                            // Call C# compent to unzip the specified zipfile to a folder
                            upZipFile(localFile, unzipFolder);
                        });
                    });

                    return;
                }
            }, error);
        };

        // On application activation, reassign callbacks for a download
        // operation persisted from previous application state.
        this.load = function (loadedDownload) {
            download = loadedDownload;
            promise = download.attachAsync().then(complete, error, progress);
        };
}

when i restart my app getcurrentdownloadASync working fine,this.load function reassign the callbacks to download but where to call extraction method when i reattach my transfer download,how to pass the arguements to this.load() function

 

Windows.Networking.BackgroundTransfer.BackgroundDownloader.getCurrentDownloadsAsync().done(function (downloads) {
                    // If downloads from previous application state exist, reassign callbacks and persist to global array.
                    if (downloads) {
                        Log("Loading background downloads: " + downloads.size);
                        console.log("download size:" + downloads.size);
                        for (var i = 0; i < downloads.size; i++) {
                            var download = new DownloadOperation();
                            download.load(downloads[i]);
                            downloadOperations.push(download);
                        }
                    }
                });

Any help would be greatly appreciated