i have the following code:

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.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public class ThreadWork
        {
            public static void DoWork()
            {
                serialPort1.Open();
                serialPort1.Write("AT+CMGF=1\r\n");
                //Thread.Sleep(500);
                serialPort1.Write("AT+CNMI=2,2\r\n");
                //Thread.Sleep(500);
                serialPort1.Write("AT+CSCA=\"+4790002100\"\r\n");
                //Thread.Sleep(500);
                serialPort1.DataReceived += serialPort1_DataReceived_1;
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork);
            Thread myThread = new Thread(myThreadDelegate);
            myThread.Start();
        }

        private void serialPort1_DataReceived_1(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            string response = serialPort1.ReadLine();
            this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n")));
        }
    }
}

and for all the serialport1 lines i am getting this error:

Error 1 An object reference is required for the non-static field, method, or property 'WindowsFormsApplication1.Form1.serialPort1' C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 23 17 WindowsFormsApplication1

what am i doing wrong?