BackgroundWorker backgroundWorker1 = null; 

public Form1() 
{ 
 InitializeComponent(); 
 backgroundWorker1 = new BackgroundWorker(); 
 backgroundWorker1.WorkerReportsProgress = true;//能否報(bào)告進(jìn)度更新。 
 backgroundWorker1.WorkerSupportsCancellation = true;//是否支持異步取消 
 //綁定事件 
 backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork); 
 backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged); 
 backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted); 
} 

private void backgroundWorker1_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) 
{  
 //句柄sender指向的就是該BackgroundWorker。 
 
 //e.Argument 獲取異步操作參數(shù)的值 
 //e.Cancel 是否應(yīng)該取消事件 
 //e.Result 獲取或設(shè)置異步操作結(jié)果的值(在RunWorkerCompleted事件可能會(huì)使用到) 
 object a = e.Argument;//獲取RunWorkerAsync(object argument)傳入的值 
 BackgroundWorker worker = sender as BackgroundWorker; 
    
 for (int i = 1; i <= 10; i++) 
 { 
  if (worker.CancellationPending == true)//在耗時(shí)操作中判斷CancellationPending屬性，如果為false則退出 
  { 
   e.Cancel = true; 
   break; 
  } 
  else 
  { 
   // Perform a time consuming operation and report progress. 
   System.Threading.Thread.Sleep(500); 
   worker.ReportProgress(i * 10, "Object userState");// 將觸發(fā)BackgroundWorker.ProgressChanged事件，向ProgressChanged報(bào)告進(jìn)度 
  } 
 } 
 e.Result = "結(jié)束"; 
} 

private void backgroundWorker1_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) 
{ 
 //e.Cancelled指示異步操作是否已被取消 
 //e.Error 指示異步操作期間發(fā)生的錯(cuò)誤 
 //e.Result 獲取異步操作結(jié)果的值,即DoWork事件中，Result設(shè)置的值。 
 if (e.Cancelled == true) 
 { 
  resultLabel.Text = "Canceled!"; 
 } 
 else if (e.Error != null) 
 { 
  resultLabel.Text = "Error: " + e.Error.Message; 
 } 
 else 
 { 
  resultLabel.Text = e.Result.ToString(); 
 } 
}

private void backgroundWorker1_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e) 
{ 
 //e.ProgressPercentage 獲取異步操作進(jìn)度的百分比 
 resultLabel.Text = (e.ProgressPercentage.ToString() + "%"); 
 string state = (string)e.UserState;//接收ReportProgress方法傳遞過(guò)來(lái)的userState 
}

 //開(kāi)始按鈕 
private void btnStart_Click(object sender, EventArgs e) 
{ 
 if (backgroundWorker1.IsBusy != true)//判斷BackgroundWorker 是否正在運(yùn)行異步操作。 
 { 
  // Start the asynchronous operation. 
  backgroundWorker1.RunWorkerAsync("object argument");//啟動(dòng)異步操作，有兩種重載。將觸發(fā)BackgroundWorker.DoWork事件 
 } 
} 
 //終止 
private void btnEnd_Click(object sender, EventArgs e) 
{ 
 if (backgroundWorker1.WorkerSupportsCancellation == true) 
 { 
  // Cancel the asynchronous operation. 
  backgroundWorker1.CancelAsync(); //請(qǐng)求取消掛起的后臺(tái)操作。調(diào)用該方法將使BackgroundWorker.CancellationPending屬性設(shè)置為True。 
 } 
}