C# serialport communication for Arduino

Question

I made a little application for my Arduino in C#. Everything works fine, but the problem is in my application. The user can chose his/hers COM port in a numericUpDown.

It works, but if the user chose the wrong port and tries to connect, it crashes, so I was thinking I need an IF statmant that gives a message. For example, the wrong port, etc., but I don't know how to make it. How can I do it?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.IO.Ports;

namespace IO_Arduino_experiment_project
{
    public partial class Form1 : Form
    {
        public static System.IO.Ports.SerialPort serialPort1;
        private delegate void LineReceivedEvent(string line);
        public Form1()
        {
            InitializeComponent();
            button5.Enabled = false;
            button2.Enabled = false;
            button3.Enabled = false;
        }

        private void button1_Click(object sender, EventArgs e) // Connect Button
        {
            System.ComponentModel.IContainer components = new System.ComponentModel.Container();
            serialPort1 = new System.IO.Ports.SerialPort(components); // Creating the new object.
            serialPort1.PortName = "COM" + numericUpDown1.Value.ToString(); // Setting what port number.
            serialPort1.BaudRate = 9600;
            serialPort1.DtrEnable = true;
            serialPort1.Open(); // Open the port for use.
            button1.Text = "Connected.";
            button1.Enabled = false;
            numericUpDown1.Enabled = false;
            button5.Enabled = true;
            button2.Enabled = true;
            button3.Enabled = true;
        }

        private void numericUpDown1_ValueChanged(object sender, EventArgs e)
        {

        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (serialPort1.IsOpen) serialPort1.Close();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            serialPort1.Write("1");
            textBox1.Text = "LED is on!";
            button2.Enabled = false;
            button3.Enabled = true;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            serialPort1.Write("0");
            textBox1.Text = "LED is off!";
            button2.Enabled = true;
            button3.Enabled = false;
        }

        private void button4_Click(object sender, EventArgs e)
        {
            Close();
        }

        private void button5_Click(object sender, EventArgs e)
        {
            serialPort1.Close();
            button1.Enabled = true;
            numericUpDown1.Enabled = true;
        }
    }
}

Answer 1

You should really replace the numeric up/down with a ComboBox or some other list control/menu that populates when the form opens or when a refresh button is clicked (or by other automatic means such as a timer).

The ComboBox or List can be filled using the GetPortNames method:-

String[] pNames;
pNames = System.IO.Ports.SerialPort.GetPortNames();

If you want to do what you have described then you can lookup the port to see if it exists prior to attempted use using similar code:-

if (System.IO.Ports.SerialPort.GetPortNames().indexOf("COM" +  thePortNum.ToString())>-1)

Note thatGetPortNames() returns a list like this:-

 COM1
 COM10
 COM12