BackgroundWorker線程不會停止winforms c＃

Question

我正在使用BackgroundWorker線程調用一個小例程，它接收來自MSMQ的消息，一旦消息到達MSMQ隊列（消息到達msmq，每隔5秒）它涉及到我的應用程序這是使用BackgroundWorker線程。以下是我的Win Form類。我是線程的新手，所以如果我做錯了什麼，請請諒解

問題：我的應用程序是MDI應用程序，當我第一次執行我的應用程序時，它工作得很好，一收到MSMQ消息，隊列，這是每5秒，但是當我關閉這個表單時，它是一個子表單，它關閉的很好，但是在打開同樣的表單後，我正在接收來自MSMQ的消息，並持續了10秒的達賴，所以這意味着我正在搞亂一些東西在後臺工作線程中，我試圖取消這個後臺工作線程，但是我失敗了，無法正確地執行或終止線程。請幫助並分享您的體驗。下面是我的表單代碼。

public partial class FrmBooking : BookingManager.Core.BaseForm.BaseForm 
{ 
    internal const string queName = @"messageServer\private$\Response"; 
    private Int32 counter = 0; 
    BackgroundWorker backgroundWorker1 = new BackgroundWorker(); 


    public FrmBooking() 
    { 
     InitializeComponent(); 
     backgroundWorker1.WorkerReportsProgress = true; 
     backgroundWorker1.WorkerSupportsCancellation = true; 
     backgroundWorker1.RunWorkerCompleted+=new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted); 
     backgroundWorker1.ProgressChanged+=new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged); 
     backgroundWorker1.DoWork+=new DoWorkEventHandler(backgroundWorker1_DoWork); 

    }   

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) 
    { 
     BackgroundWorker bgWorker = sender as BackgroundWorker; 

     if (bgWorker.CancellationPending) 
     { 
      e.Cancel = true; 
      return; 
     } 


      try 
      { 

       MessageQueue messageQueue = null; 
       if (MessageQueue.Exists(queName)) 
       { 
        messageQueue = new MessageQueue(queName); 
       } 
       else 
       { 
        MessageQueue.Create(queName); 
       } 

       messageQueue.Formatter = new XmlMessageFormatter(new Type[] { typeof(String) }); 

       System.Messaging.Message msg = messageQueue.Receive(); 



       bgWorker.ReportProgress(100, msg); 

      } 
      catch (Exception ex) { } 


    } 
    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     if (!e.Cancelled) 
     { 
      backgroundWorker1.RunWorkerAsync(); 
     } 


    } 
    private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e) 
    { 

     System.Messaging.Message msg = e.UserState as System.Messaging.Message; 

     listBoxControl1.Items.Add(msg.Body.ToString()); 
     counter++; 
     labelControl1.Text = String.Format("Total messages received {0}", counter.ToString()); 
    } 

    private void FrmBooking_Load(object sender, EventArgs e) 
    { 
     backgroundWorker1.RunWorkerAsync(); 

    } 
} 

Answer 1

當您關閉表單時，您是否終止工作人員？如果沒有，如果有表單的引用或某個地方的工作人員（事件處理程序？），那麼它將不會得到GCd並停留在附近。當打開第二個實例可能運行兩個後臺工作者....

Answer 2

你這裏有兩種選擇：

1）在窗體的Closing事件，呼籲backgroundWorker1。 CancelAsync（）。

2）更好的方法是完全刪除你的後臺工作者，並使用MessageQueue的本地異步處理機制。添加ReceivedCompleted事件處理程序後，您可以使用BeginReceive方法啓動隊列請求，然後在完成的事件處理程序中處理消息並重新啓動請求。

問題是，如果您發出接收請求，它將阻塞後臺工作線程，直到隊列中收到一條消息，並且CancelAsync只會請求後臺工作者停止，它不會取消接收請求。

例如（更新）：

public partial class FrmBooking : BookingManager.Core.BaseForm.BaseForm 
{ 
    public FrmBooking() 
    { 
     InitializeComponent(); 

     this.FormClosing += new FormClosingEventHandler(FrmBooking_FormClosing); 
    } 

    internal const string queName = @"messageServer\private$\Response"; 
    private Int32 counter = 0; 
    private MessageQueue messageQueue = null; 

    private bool formIsClosed = false; 

    private void FrmBooking_Load(object sender, EventArgs e) 
    { 
     StartQueue(); 
    } 

    void FrmBooking_FormClosing(object sender, FormClosingEventArgs e) 
    { 
     // Set the flag to indicate the form is closed 
     formIsClosed = true; 

     // If the messagequeue exists, close it 
     if (messageQueue != null) 
     { 
      messageQueue.Close(); 
     } 
    } 

    private void StartQueue() 
    { 
     if (MessageQueue.Exists(queName)) 
     { 
      messageQueue = new MessageQueue(queName); 
     } 
     else 
     { 
      MessageQueue.Create(queName); 
     } 

     messageQueue.Formatter = new XmlMessageFormatter(new Type[] { typeof(String) }); 

     // Add an event handler for the ReceiveCompleted event. 
     messageQueue.ReceiveCompleted += new ReceiveCompletedEventHandler(MessageReceived); 

     messageQueue.BeginReceive(TimeSpan.FromSeconds(15)); 
    } 

    // Provides an event handler for the ReceiveCompleted event. 
    private void MessageReceived(Object source, ReceiveCompletedEventArgs asyncResult) 
    { 
     if (!this.formIsClosed) 
     { 
      // End the asynchronous receive operation. 
      System.Messaging.Message msg = messageQueue.EndReceive(asyncResult.AsyncResult); 

      // Display the message information on the screen. 
      listBoxControl1.Items.Add(msg.Body.ToString()); 
      counter++; 
      labelControl1.Text = String.Format("Total messages received {0}", counter.ToString()); 

      // Start receiving the next message 
      messageQueue.BeginReceive(TimeSpan.FromSeconds(15)); 
     } 
    } 

}