1: private static int MaxRecords = 100;

   1: private void buttonStartLeft_Click(object sender, EventArgs e)

   2: {

   3:     if (this.backgroundWorkerLeft.IsBusy)

   4:     {

   5:         return;

   6:     }

   7:     this.listBoxLeft.Items.Clear();

   8:     this.backgroundWorkerLeft.RunWorkerAsync(MaxRecords);

   9:     this.buttonStartLeft.Enabled = false;

  10:     this.buttonCacnelLeft.Enabled = true;

  11: } 

   1: private void backgroundWorkerLeft_DoWork(object sender, DoWorkEventArgs e)

   2: {

   3:     try

   4:     {

   5: e.Result = this.RetrieveData(this.backgroundWorkerLeft, e);

   6:     }

   7:     catch (Exception ex)

   8:     {

   9:        MessageBox.Show(ex.Message);

  10:        throw;

  11:     }

  12: } 

   1: private int RetrieveData(BackgroundWorker worker, DoWorkEventArgs e)

   2: {

   3:     int maxRecords = (int)e.Argument;

   4:     int percent = 0;

   5:     for (int i = 1; i <= maxRecords; i++)

   6:     {

   7:         if (worker.CancellationPending)

   8:         {

   9:             return i;

  10:         } 

  11:  

  12:         percent = (int)(((double)i / (double)maxRecords) * 100);

  13:         worker.ReportProgress(percent, new KeyValuePair<int,string>(i,Guid.NewGuid().ToString()));

  14:         Thread.Sleep(100);

  15:     } 

  16:  

  17:     return maxRecords;

  18: } 

   1: private void backgroundWorkerLeft_ProgressChanged(object sender, ProgressChangedEventArgs e)

   2: {

   3:     KeyValuePair<int,string> record = (KeyValuePair<int,string>) e.UserState ;

   4:     this.labelResultLeft.Text = string.Format("There are {0} records retrieved!", record.Key);

   5:     this.progressBarLeft.Value = e.ProgressPercentage;

   6:     this.listBoxLeft.Items.Add(record.Value);

   7: }

   1: private void buttonCacnelLeft_Click(object sender, EventArgs e)

   2: {

   3:     this.backgroundWorkerLeft.CancelAsync();

   4: } 

   1: private void backgroundWorkerLeft_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

   2: {

   3:     try

   4:     {

   5:         this.labelResultLeft.Text = string.Format("Total records: {0}", e.Result);

   6:         this.buttonStartLeft.Enabled = true;

   7:         this.buttonCacnelLeft.Enabled = false;

   8:     }

   9:     catch (TargetInvocationException ex)

  10:     {

  11:         MessageBox.Show(ex.InnerException.GetType().ToString());

  12:     }

  13: }