如何使用backgroundworker更新GUI？

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace BackgroundWorkerExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            backgroundWorker1.WorkerReportsProgress = true;
            backgroundWorker1.WorkerSupportsCancellation = true;
            backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
            backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
            backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (backgroundWorker1.IsBusy != true)
            {
                backgroundWorker1.RunWorkerAsync();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (backgroundWorker1.WorkerSupportsCancellation == true)
            {
                backgroundWorker1.CancelAsync();
            }
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            for (int i = 1; i <= 10; i++)
            {
                if (worker.CancellationPending == true)
                {
                    e.Cancel = true;
                    break;
                }
                else
                {
                    Thread.Sleep(1000);
                    worker.ReportProgress(i * 10);
                }
            }
        }

        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage;
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled == true)
            {
                MessageBox.Show("Task cancelled.");
            }
            else if (e.Error != null)
            {
                MessageBox.Show("Error while performing background operation.");
            }
            else
            {
                MessageBox.Show("Task completed successfully.");
            }
        }
    }
}