public partial class Form1 : Form
    {
 
        public Form1()
        {
            InitializeComponent();
            this.backgroundWorker1.WorkerSupportsCancellation = true;
            this.backgroundWorker1.WorkerReportsProgress = true;
 
            this.backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
            this.backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
            this.backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
 
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            if (this.textBox1.Text != "" && this.textBox2.Text != "")
            {
                ab a = new ab(int.Parse(this.textBox1.Text), int.Parse(this.textBox2.Text));
                this.backgroundWorker1.RunWorkerAsync(a);
            }
 
        }
 
        private void button2_Click(object sender, EventArgs e)
        {
            this.backgroundWorker1.CancelAsync();
        }
 
        void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            this.progressBar1.Value = e.ProgressPercentage;
        }
 
        void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
            {
                this.textBox3.Text = "Result :Canclled!";
                this.progressBar1.Value = 100;
            }
            else if (e.Error != null)
            {
                MessageBox.Show("Error Details : " + (e.Error as Exception).ToString());
            }
            else
            {
                    this.textBox3.Text = "Result :" + e.Result;
                    this.progressBar1.Value = 100;
             }
        }
 
        void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            //do something here backgroundly.
 
                for (int i = 0; i < this.progressBar1.Maximum; i++)
                {
                    Thread.Sleep(50);
                    this.backgroundWorker1.ReportProgress(i);
 
                    if (this.backgroundWorker1.CancellationPending)
                    {
                        e.Cancel = true;
                        return;
                    }
 
                }
                ab a = (ab)e.Argument;
                e.Result = a.C;
 
            }
 
    }
 
    class ab
    {
        private int _a;
 
        public int A
        {
            get { return _a; }
            set { _a = value; }
        }
        private int _b;
 
        public int B
        {
            get { return _b; }
            set { _b = value; }
        }
        public ab(int a,int b)
        {
            this._a = a;
            this._b = b;
        }
 
        public int C
        {
            get { return _b + _a; }
        }
    }