Keeping variable values in a class

Question

I am creating a UWP application that will need to communicate with multiple modules (Rduino) by RS485.

At this time and for testing I created a small application that communicates with any of these modules without problems.

My problem is that my application will have more than one Page and to effect these communications I thought to create a class to always keep the communications working.

The problem is that this way I can’t keep the connection active, that is, after starting the communication, it loses the state of it.

Communications are initiated through this function:

private async Task initComm()
    {
        try
        {
            //cParam = PDB.getParameters();
            string selectedPortID = null;
            string aqs = SerialDevice.GetDeviceSelector();
            deviceInformation = await DeviceInformation.FindAllAsync(aqs);
            foreach (var devInfo in deviceInformation)
            {
                if (devInfo.Name == "USB-RS485 Cable")
                {
                    selectedPortID = devInfo.Id;
                }
            }

            serialPort = await SerialDevice.FromIdAsync(selectedPortID);


            if (serialPort != null)
            {
                serialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
                serialPort.BaudRate = 9600; 
                serialPort.Parity = SerialParity.None; 
                serialPort.StopBits = SerialStopBitCount.One;
                serialPort.DataBits = 8;
            }
            else
            {
                var status = DeviceAccessInformation.CreateFromId(selectedPortID).CurrentStatus;
                // ELDB.attachEvent("E1002", "Starting Comunication Failed: " + status.ToString());
            }
            while (flagComm)
            {
                try
                {
                    await Listen();
                }
                catch (Exception ex)
                {
                    // ELDB.attachEvent("E2cC", ex.Message);
                }

            }
        }
        catch (Exception ex)
        {
            // ELDB.attachEvent("E1cC", ex.Message);
        }
    }

When I try to send something, through this method:

private async void writeComm(string str2send)
    {
        try
        {
            using (var dataWriter = new DataWriter(serialPort.OutputStream))
            {
                dataWriter.WriteString(str2send);
                await dataWriter.StoreAsync();
                await dataWriter.FlushAsync();
                dataWriter.DetachStream();
            }
        }
        catch (Exception ex)
        {
            eventLog = ex.Message;
            // ELDB.attachEvent("E6cC", ex.Message);
        }
    }

What happens is that it enters into exception because the referenced object no longer exists...

As shown in the image, "serialPort == null"

What I would like to know is whether it is possible to maintain this idea of having a class with the methods and just call them when I want to send something, or if I have to change the thinking.

In case you’re the second, any idea how this works?

Answer 1

From what I understand you want to keep the data fixed? (Ñ have to pass the information every time you make the calls) If this is your case, the solution is quite simple!

Declare your Serial Port as Static

static serialPort Porta = await SerialDevice.FromIdAsync(selectedPortID);

Once this is done, when you set the information as, Port, Baudrate, Readtimeout and etc, this information is fixed in the configuration of your series, and can be used in other methods and/or classes(Depending on the privacy set, for cases where other classes will access the serial port, I recommend leaving it as private and use Get/Set methods to set your information!)