C#中用WriteFile向串口发指令问题

Question

在c#里使用api函数向串口发指令时，每次写串口成功都要1秒钟，哪位高人指点下是什么问题。串口类是网上下载的JustinIO

Answer 1

写串口的函数 
public void Write(byte[] WriteBytes)
        {
            if (hComm != INVALID_HANDLE_VALUE)
            {
                OVERLAPPED ovlCommPort = new OVERLAPPED();
                int BytesWritten = 0;
                WriteFile(hComm, WriteBytes, WriteBytes.Length, ref BytesWritten, ref ovlCommPort);
            }
            else
            {
                throw (new ApplicationException("串口未打开！"));
            }
        }

Answer 2

发的字符不论多少都会有这个问题，网上说JustinIO这个类是异步的呀。