serial port in c#

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.Ports;

namespace serial_port
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string[] ports = SerialPort.GetPortNames();
            foreach(string port in ports)
            {
                comboBox1.Items.Add(port);
            }
        }

        string t;
        private void button2_Click(object sender, EventArgs e)
        {
            
                t= comboBox1.Text.ToString();
            sErial(t);
        }

        void sErial(string Port_name)
        {
            SerialPort sp = new SerialPort(Port_name, 9600, Parity.None, 8, StopBits.One);
            sp.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);
            sp.Open();
        }
        private void ReceivedHandrler (object sender,SerialDataReceivedEventArgs e )
        {
            SerialPort sp = (SerialPort)sender;
            string w = sp.ReadLine();
            if(w != string.Empty)
            {
                invoke(new Action (()=>richTextbox1.AppendText(w) ));
            }

        }
    }
}

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