/// <summary>  /// 根据GUID获取16位的唯一字符串  /// </summary>  /// <param name=\"guid\"></param>  /// <returns></returns>  public static string GuidTo16String()  {      long i = 1;      foreach (byte b in Guid.NewGuid().ToByteArray())          i *= ((int)b + 1);      return string.Format(\"{0:x}\", i - DateTime.Now.Ticks);  }  /// <summary>  /// 根据GUID获取19位的唯一数字序列  /// </summary>  /// <returns></returns>  public static long GuidToLongID()  {      byte[] buffer = Guid.NewGuid().ToByteArray();      return BitConverter.ToInt64(buffer, 0);  }