/// <summary>
        /// 每秒触发事件(下载速度计算)
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            DownloadSpeedChangedArg arg = new DownloadSpeedChangedArg
            {
                SizePerSec = _downloadSizePerSec
            };

            if (_downloadSizePerSec > 1048576)
            {
                arg.SpeedUnit  = "MB/s";
                arg.SpeedValue = Math.Round((decimal)_downloadSizePerSec / (decimal)1048576, 2);
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            else if (_downloadSizePerSec > 1024)
            {
                arg.SpeedUnit  = "KB/s";
                arg.SpeedValue = Math.Round((decimal)_downloadSizePerSec / (decimal)1024, 2);
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            else
            {
                arg.SpeedUnit  = "B/s";
                arg.SpeedValue = _downloadSizePerSec;
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            _downloadSizePerSec = 0;
        }
        private void _timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            DownloadSpeedChangedArg arg = new DownloadSpeedChangedArg();

            if (_downloadSizePerSec > 1048576)
            {
                arg.SpeedUnit  = "MB/s";
                arg.SpeedValue = _downloadSizePerSec / 1048576;
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            else if (_downloadSizePerSec > 1024)
            {
                arg.SpeedUnit  = "KB/s";
                arg.SpeedValue = _downloadSizePerSec / 1024;
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            else
            {
                arg.SpeedUnit  = "B/s";
                arg.SpeedValue = _downloadSizePerSec;
                DownloadSpeedChanged?.Invoke(this, arg);
            }
            _downloadSizePerSec = 0;
        }