Com port c#, windows form

Jan 1947

Hi Guys,
I am not expert and will be glad to get some help. I wrote software, where I am using Barcode reader, com port, in number of Windows forms. I am switching receive data on Form Activation and disabling it on Form deactivated. it has worked well for number of months, but now I am occasionally get error, Com port is not accessible. Received I use Invoke.

    private void CheckForUsbDevice()
    {

        string\[\] ports = SerialPort.GetPortNames();

        // Display each port name to the console.
        foreach (string port in ports)
        {
            if ((port == "COM3") || (port == "COM4"))
            {
                if (AcdStart.mySerialPort == null)
                {
                    AcdStart.mySerialPort = new SerialPort(port)
                    {
                        BaudRate = 9600,
                        Parity = Parity.None,
                        StopBits = StopBits.One,
                        DataBits = 8,
                        Handshake = Handshake.None,
                        RtsEnable = true
                    };
                }
                     AcdStart.mySerialPort.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);
                if (!AcdStart.mySerialPort.IsOpen)
                {
                    AcdStart.mySerialPort.Close();
                    AcdStart.mySerialPort.Open();
                }
                    PortTextBox.Text = (string.Format("Port {0}", port));
                break;
            }
        }
    }

    private void RxPurchaseOrder\_Deactivate(object sender, System.EventArgs e)
    {
        if ((AcdStart.mySerialPort != null) && (AcdStart.mySerialPort.IsOpen))
            AcdStart.mySerialPort.DiscardInBuffer();

        if (AcdStart.mySerialPort != null)
        {
            AcdStart.mySerialPort.DataReceived -= new SerialDataReceivedEventHandler(DataReceivedHandler);
            AcdStart.mySerialPort.Close();
        }
        AcdStart.mySerialPort = null;
        PauseNow = true;
        this.BackColor = Color.LightSalmon;
    }

    private void RxPurchaseOrder\_Activated(object sender, EventArgs e)
    {
        if ((AcdStart.mySerialPort != null) && (AcdStart.mySerialPort.IsOpen))
        {
            AcdStart.mySerialPort.DiscardInBu

Lost User

What is the exact error message, and where is it generated?

Lost User

You have a "number of forms", and imply that each form is opening and closing the port on activation / deactivation. I maintain the serial port should not be dependent on "forms"; and should be part of the app's start and stop process (and "interval" / wait processing). The port should be "wrapped" in such a way that it can be shared by the various forms / processes.

"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I

Jan 1947

Hi Garry thanks for your reply. As I was unable to find some example, this is how I have created. I feel it is not good way, as I done it, as there is a lot of areas which is unpredictable. I will try to see. what I can do. If you have some link to give me some link to example, will be very much appreciated. I fully agree with Napoleon and like the internet and Code Project, to learn. thanks for great help. Regards John

Jan 1947

Hi Richard The error is, "Access to com port denied". as it is very hard to debug it but it happens on Open port call. I have done some changes, leave com port assigned and only remove or add SerialDataRceivedEventHandler. I feel it is still not the good way, but is working. regards John

Lost User

One picks what's most comfortable after looking around. [https://stackoverflow.com/questions/2799856/c-sharp-serial-port-driver-wrapper-class-code-and-concept-quality\](https://stackoverflow.com/questions/2799856/c-sharp-serial-port-driver-wrapper-class-code-and-concept-quality)

"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I

Jan 1947

thank you Gerry regards John