BackgroundWorker线程不会停止winforms c＃

Question

我正在使用BackgroundWorker线程调用一个小例程，它接收来自MSMQ的消息，一旦消息到达MSMQ队列（消息到达msmq，每隔5秒）它涉及到我的应用程序这是使用BackgroundWorker线程。以下是我的Win Form类。我是线程的新手，所以如果我做错了什么，请请谅解

问题：我的应用程序是MDI应用程序，当我第一次执行我的应用程序时，它工作得很好，一收到MSMQ消息，队列，这是每5秒，但是当我关闭这个表单时，它是一个子表单，它关闭的很好，但是在打开同样的表单后，我正在接收来自MSMQ的消息，并持续了10秒的达赖，所以这意味着我正在搞乱一些东西在后台工作线程中，我试图取消这个后台工作线程，但是我失败了，无法正确地执行或终止线程。请帮助并分享您的体验。下面是我的表单代码。

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

当您关闭表单时，您是否终止工作人员？如果没有，如果有表单的引用或某个地方的工作人员（事件处理程序？），那么它将不会得到GCd并停留在附近。当打开第二个实例可能运行两个后台工作者....

Answer 2

你这里有两种选择：

1）在窗体的Closing事件，呼吁backgroundWorker1。 CancelAsync（）。

2）更好的方法是完全删除你的后台工作者，并使用MessageQueue的本地异步处理机制。添加ReceivedCompleted事件处理程序后，您可以使用BeginReceive方法启动队列请求，然后在完成的事件处理程序中处理消息并重新启动请求。

问题是，如果您发出接收请求，它将阻塞后台工作线程，直到队列中收到一条消息，并且CancelAsync只会请求后台工作者停止，它不会取消接收请求。

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)); 
     } 
    } 

}