Question

我正在使用后台工作程序来监听UDP然后进行处理。我想点击button2

时退出

  public snmpmain()
    {
        InitializeComponent();
        backsnmp = new BackgroundWorker();
        backsnmp.DoWork += new DoWorkEventHandler(backsnmp_DoWork);
        backsnmp.ProgressChanged += new ProgressChangedEventHandler
               (backsnmp_ProgressChanged);
        backsnmp.WorkerReportsProgress = true;
        _startsnmp = true;
        backsnmp.WorkerSupportsCancellation = true;


    }

private void button1_Click(object sender, EventArgs e)
    {
        button1.Enabled = false;
        this.backsnmp.RunWorkerAsync();
      }

    private void button2_Click(object sender, EventArgs e)   
       /* it executes this when button2 is pressed but nothing happens. I can receive the UDP packets the dowork hasn't stopped*/
    {
        _startsnmp = false;
        backsnmp.CancelAsync();
        listBox1.Items.Add("SNMP Stopped");

        }

 void backsnmp_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        listBox1.Items.Add (e.UserState as String);        
     }

  void backsnmp_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (e.Cancelled)
        {
            listBox1.Items.Add("SNMP Stopped");
            button2.Enabled = false;
            button1.Enabled = true;
        }
    }

  void backsnmp_DoWork(object sender, DoWorkEventArgs e)
    {

        backsnmp.ReportProgress(0, "Initializing SNMP Listener on Port:" + port + "...");
             UdpClient listener = new UdpClient(port);
            IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, port);

            while (true)
            {

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


                   Thread.Sleep(100);


                    backsnmp.ReportProgress(0, "Waiting for messages....");

       packet = listener.Receive(ref groupEP);   // When I press button2 it's right here


                  // do some work here

当我点击button2时它会执行button2_Click，但没有真正发生。 dowork没有被取消。我仍然可以收到数据包。

Answer 1

listener.Receive阻止，直到收到数据。因此，您的取消根本不被承认。

你可以做的是使用BeginReceive（并摆脱BackgroundWorker）或尝试使listener成为一个类字段并在取消时将其处理掉。后者应该留下阻塞接收但有例外。好吧 - 或者在取消后自己向听众发送消息（显然也会唤醒接收者）。

c＃后台工作人员不退出

1 个答案: