Question

How we know with SerialPort class in c# when we receive all the data from the device connected on the serial port ?

There is my code. How i know i received all the data from the device ?

private void button1_Click(object sender, RoutedEventArgs e)
        {
    p = new SerialPort("COM5");
                if (!p.IsOpen)
                {
                    try
                    {
                        p.Open();
                        p.DataReceived += new SerialDataReceivedEventHandler(p_DataReceived);
                        p.PinChanged += new SerialPinChangedEventHandler(p_PinChanged);                       
                      Data = "Port ouvert";
                    }
                    catch (Exception ex)
                    {
                        Data = string.Format("Erreur ouverture du port : {0}", ex.Message);
                    }
                }}


    void p_DataReceived(object sender, SerialDataReceivedEventArgs e)
            {

                var serial = (SerialPort)sender;

                string line = serial.ReadExisting();

                string data =  string.Format("Donné recu : {0}",line);          
                Data = data;
                strb.Append(line);

            }

Answer 1

how do you imagine to have received all data? The device can always send you some more later.

For example we had a medical device which used to send lines of text to a serially connected printer (one of those old pins printers able to print one line at time and keep on the same page), we replaced the printer with a computer and made a software able to append in a TextArea the lines of text as they came from the Serial port.

in this way, you should listen to the serial port and detect a new line terminated with the proper line break code and handle that new line but you do have to stay connected and see if other data is coming afterwards.

I would say it depends on your device if you know that once it completes a certain operation will send you a special code then check for that code, otherwise just stay connected and listen to all incoming data.