/// <summary>
 /// Gets the XSH a256 asynchronous.
 /// </summary>
 /// <param name="client">The client.</param>
 /// <param name="path">The path.</param>
 /// <param name="factory">The factory.</param>
 /// <param name="creationOptions">The creation options.</param>
 /// <param name="scheduler">The scheduler.</param>
 /// <returns></returns>
 public static Task <string> GetXSHA256Async(this FtpClient client, string path,
                                             TaskFactory <string> factory        = null,
                                             TaskCreationOptions creationOptions = default(TaskCreationOptions),
                                             TaskScheduler scheduler             = null)
 {
     return((factory = factory ?? Task <string> .Factory).FromAsync(
                client.BeginGetXSHA256(path, null, null),
                XSHA256.EndGetXSHA256,
                creationOptions, scheduler ?? factory.Scheduler ?? TaskScheduler.Current));
 }