VS C＃列表可用（未使用）串行端口

Question

I am writing my first ever program in C# using Visual Studio, I have a function that populates a dropdown with 'available' COM ports. How do I check if one of these 'available' ports is not open outside of my program?

    foreach (string portName in System.IO.Ports.SerialPort.GetPortNames())
    {
        serialPort1.PortName = portName;
        if (serialPort1.IsOpen == false) // Only list if it is not in use - does not work - .IsOpen is only valid from within this app
        {
            CommsBox.Items.Add(portName);
        }
    }

I hoped to do this but it does not work.

Answer 1

When you initialize serialPort1 ?

You should create a new instance of SerialPort , and open it to know if it's free like this:

foreach (string portName in System.IO.Ports.SerialPort.GetPortNames())
    {
        try{
            SerialPort serialPort1 = new SerialPort();
            serialPort1.PortName = portName;
            serialPort1.Open();
            CommsBox.Items.Add(portName); //If you can open it it's because it was free, so we can add it to available
            serialPort1.Close(); //Should close it again
            }
        catch (Exception ex){
            //manage the exception...
        }
    }

More information about 'SerialPort' class

EDIT:

The best solution is follow @Baddack comment:

"Hans Passant said it the best: "Such code can never work reliably on a multi-tasking operating system. You cannot find out until you call Open(). At which point you get a crystal-clear exception.". You should really just populate the combobox with all the COM ports and let the user decide. If the COM port is in use, then a exception is thrown and you can handle that however you please."