Why SerialPort.DataReceived event causes error "Access to the path COM4 is denied

I am working on a C# program to communicate with Arduino through serial port. I used this code to receive data and write it in console:

using System;
using System.IO.Ports;


while (true)
{
    SerialPort serialPort = new SerialPort();
    serialPort.PortName = "COM4";
    serialPort.BaudRate = 9600; 
    serialPort.Parity = Parity.None;
    serialPort.DataBits = 8;
    serialPort.StopBits = StopBits.One;
    serialPort.Handshake = Handshake.None;
    serialPort.DataReceived += SerialPortDataReceived;
    try
    {
        serialPort.Open();
    }
    catch (Exception ex)
    {
        Console.WriteLine("Error: " + ex.Message);
    }

    void SerialPortDataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        SerialPort sp = (SerialPort)sender;
        string data = sp.ReadExisting();
        Console.WriteLine("Received data: " + data);
    }

}

But this error happened:
Access to the path ‘COM4’ is denied.

I checked again the settings (such as port name etc.). And the settings were correct.
Also, no other application was using this port.
After that I tried this code in similar situation and it worked fine:

using System.IO.Ports;
SerialPort serialPort = new SerialPort();
serialPort.PortName = "COM4";
serialPort.BaudRate = 9600;
serialPort.Parity = Parity.None;
serialPort.DataBits = 8;
serialPort.StopBits = StopBits.One;
serialPort.Handshake = Handshake.None;
try
{
    serialPort.Open();
}
catch (Exception ex)
{

    Console.WriteLine("Error: " + ex.Message);
}

while (true)
{

    string a = serialPort.ReadExisting();
    Console.WriteLine(a);
    Thread.Sleep(200);

}

Why does the first code not work and is there a way I can use the first method?

>Solution :

Well, look at your first code…

You use a loop, trying to open the serial port COM4 again, and again, and again, and again, and again, and again, and again, and again, and again, and again, and again…

But of course that doesn’t happen because you can’t open the same COM port more than once unless you close it before opening it again a second time. What happens is that if you try to open a COM port again when it is already open is the operating system saying "Na-Ah!" to you in the form of the exception you observed.

Therefore the answer to one of your questions: "is there a way I can use the first method?" would basically be: What’s the point of trying to repeatedly open the same COM port? Just open it once and be happy…