Question

我希望从一个大局域中获得活着或死亡的IP地址。但需要这么多次。我决定在这里使用backgroundworker是我的代码：

try
{

    this.Status.Text = "Collecting Information...";

    if(this.TxtWorkGroup.Text.Trim() == "")
    {
        MessageBox.Show("The Work Group name Should Not be Empty");
        return;
    }


    // Use Your work Group WinNT://&&&&(Work Group Name)
    DirectoryEntry DomainEntry = new DirectoryEntry("WinNT://" + this.TxtWorkGroup.Text.Trim());
    DomainEntry.Children.SchemaFilter.Add("computer");


    // To Get all the System names And Display with the Ip Address
    foreach(DirectoryEntry machine in DomainEntry.Children)
    {
        string[] Ipaddr = new string[3];
        Ipaddr[0] = machine.Name;


        System.Net.IPHostEntry Tempaddr = null;

        try
        {
            Tempaddr = (System.Net.IPHostEntry)Dns.GetHostByName(machine.Name);
        }
        catch(Exception)
        {
            //MessageBox.Show("Unable to connect woth the system :" + machine.Name );
                        deadHostList.Items.Add(machine.Name);
            continue;
        }
        System.Net.IPAddress[] TempAd = Tempaddr.AddressList;
        foreach(IPAddress TempA in TempAd)
        {
            Ipaddr[1] = TempA.ToString();

            byte[] ab = new byte[6];
            int len = ab.Length;

            // This Function Used to Get The Physical Address
            int r = SendARP( (int) TempA.Address, 0, ab, ref len );
            string mac = BitConverter.ToString( ab, 0, 6 );

            Ipaddr[2] = mac;
        }           

        System.Windows.Forms.ListViewItem TempItem = new ListViewItem(Ipaddr);

        this.ListHostIP.Items.Add(TempItem);
    }

    this.Status.Text = "Displayed";
}
catch(Exception ex)
{
    MessageBox.Show(ex.Message,"Error",System.Windows.Forms.MessageBoxButtons.OK  );
    Application.Exit();
}

但是当我尝试在backgroundWorker1_DoWork事件中使用这些代码时，它会给出错误消息

跨线程操作无效：控制从其创建的线程以外的线程访问的“deadHostList”

如何修改我的代码？

Answer 1

您不能也不应该从创建控件的线程以外的任何线程访问UI控件。我猜你的deadHostList是一个ListView控件或类似的东西。

您可以使用Control.Invoke或Control.BeginInvoke

将后台线程中的请求封送到UI线程

Answer 2

正如克里斯和里德所说....你只能从创建控件的线程修改一个Ui控件...

您还可以使用BackgroundWorker的ProgressChanged事件进行Ui更新....

  var worker = new BackgroundWorker()
  {
    WorkerReportsProgress = true,
    WorkerSupportsCancellation = true
  };

  /// runs on background thread
  worker.DoWork += (s, e) =>
  {
    while (!done)
    { 
      DoSomeWork();
      // send a message to the Ui
      // via the ProgressChanged event
      worker.ReportProgress(percent, statusMessage); 
    }
  };

  /// the ProgressChanged event runs on the UI thread
  worker.ProgressChanged += (s, e) =>
  {
    var msg = (MyStatusMessage)e.UserState;
    someUiControl.Items.Add(msg.Text);
  };

  /// also runs on Ui thread
  worker.RunWorkerCompleted += (s, e) =>
  {

  };

  worker.RunWorkerAsync();

Answer 3

您需要始终将对UI元素的调用（例如列表控件）封送到UI线程上。

您可以通过Control.Invoke执行此操作。改变这个：

deadHostList.Items.Add(machine.Name);

要：

string name = machine.Name;
deadHostList.Invoke(new Action( () => deadHostList.Items.Add(name)));

您还需要稍后为ListHostIP执行相同的操作 - 确保使用Control.Invoke来包装该调用。

使用backgroundworker控件在局域网上获取IP地址

3 个答案: