protected void Task_ZlgClearReceiveBuffer()
{
  ZCAN_Receive_Data[] can_data = new ZCAN_Receive_Data[10];
  ZCAN_ReceiveFD_Data[] canfd_data = new ZCAN_ReceiveFD_Data[10];

  uint len;
  Thread.Sleep(1000);

  len = Method.ZCAN_GetReceiveNum(VAR_ZlgUsbCanChannelHandle, 0); // TYPE_CAN
  Console.WriteLine("ZLG USBCAN archived CAN frames are: " + len.ToString());
  ...

protected void Task_ZlgClearReceiveBuffer()
{
  ZCAN_Receive_Data[] can_data = new ZCAN_Receive_Data[10];
  ZCAN_ReceiveFD_Data[] canfd_data = new ZCAN_ReceiveFD_Data[10];

  uint len;
  Thread.Sleep(1000);

  len = Method.ZCAN_GetReceiveNum(VAR_ZlgUsbCanChannelHandle, 0); // TYPE_CAN
  Console.WriteLine("ZLG USBCAN archived CAN frames are: " + len.ToString());

  if (len > 0)
  {
    int size = Marshal.SizeOf(typeof(ZCAN_Receive_Data));
    IntPtr ptr = Marshal.AllocHGlobal((int)len * size);
    len = Method.ZCAN_Receive(VAR_ZlgUsbCanChannelHandle, ptr, len, 50);
    //for (int i = 0; i < len; ++i)
    //{
    //    // Drop the message
    //    can_data[0] = (ZCAN_Receive_Data)Marshal.PtrToStructure(
    //        (IntPtr)((Int64)ptr + i * size), typeof(ZCAN_Receive_Data));
    //}
    // OnRecvCANDataEvent(can_data, len);
    Marshal.FreeHGlobal(ptr);
  }

  len = Method.ZCAN_GetReceiveNum(VAR_ZlgUsbCanChannelHandle, 1); // TYPE_CANFD
  Console.WriteLine("ZLG USBCAN archived CAN-FD frames are: " + len.ToString());
  if (len > 0)
  {
    int size = Marshal.SizeOf(typeof(ZCAN_ReceiveFD_Data));
    IntPtr ptr = Marshal.AllocHGlobal((int)len * size);
    len = Method.ZCAN_ReceiveFD(VAR_ZlgUsbCanChannelHandle, ptr, len, 50);
    //for (int i = 0; i < len; ++i)
    //{
    //    // Drop the message
    //    canfd_data[0] = (ZCAN_ReceiveFD_Data)Marshal.PtrToStructure(
    //        (IntPtr)((Int64)ptr + i * size), typeof(ZCAN_ReceiveFD_Data));
    //}
    // OnRecvCANDataEvent(can_data, len);
    Marshal.FreeHGlobal(ptr);
  }
  Thread.Sleep(10);
}