C# Serial Port Write Byte

Question

Writing a single byte to the serial port in .NET 4.0 in C# causes a

InvalidOperationException was unhandled by user code

Every time a byte is sent to the SerialPort.

How do I write a single byte to the serial port?

    //Serial Init
    //Full fledged constuctor
    public NetCommManager(String portName, TransmissionType trans, String baud, String parity, String stopBits, String dataBits)
    {
        nc_baudRate = baud;
        nc_parity = parity;
        nc_stopBits = stopBits;
        nc_dataBits = dataBits;
        nc_portName = portName;
        nc_transType = trans;

        //now add an event handler
        comPort.DataReceived += new SerialDataReceivedEventHandler(netComm_DataReceived);
    }

Config:

       _commManger = new NetCommManager(commPortNumber,                        
       NetCommManager.TransmissionType.Text, "19200", "None", "One", "8");

The Byte to be written:

_commManager.WriteByte(Convert.ToByte( 0x7B));

And WriteByte function is:

public void WriteByte(byte data)
        {
            //change data to array
            //byte[] dataArray = new byte[1];
            var dataArray = new byte[] {data};
            //dataArray[0] = data;
            comPort.Write(dataArray, 0, 1);   // <-- Exception is thrown here
        }

The NetCommManager class is very much based on this example

You are missing portion of the code that creates comPort object... and have several commented out lines for some reason. — Alexei Levenkov
– Alexei Levenkov, Commented Jul 27, 2012 at 2:43
The commented lines are other attempts to get it working in a different form — DogEatDog
– DogEatDog, Commented Jul 27, 2012 at 2:55
+1 for good effort. Note that you still missing comPort = new... portion :). Somehow Jeff E managed to figure it (+1 to the answer obviously). On commented out code - consider if it shows significantly different variant of code. I don't think it is case here - so I'd simply remove it. — Alexei Levenkov
– Alexei Levenkov, Commented Jul 27, 2012 at 17:23

Jeff · Accepted Answer · 2012-07-27 04:57:13Z

6

You forgot to Open() the comPort: http://msdn.microsoft.com/en-us/library/ms143551.aspx

answered Jul 27, 2012 at 4:57

Jeff

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1 Comment

DogEatDog Over a year ago

This was correct. Some how the port was being closed before the Write was occurring. thanks!

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