c＃opennetCF后台工作人员 - e.result给出一个ObjectDisposedException

Question

我在C＃中使用后台工作人员。 这里是一个类，并根据它，你会发现它的instansiation，并在那里我将定义我的问题给你：

我有类图：

class Drawing 
{ 
    BackgroundWorker bgWorker; 
    ProgressBar progressBar; 
    Panel panelHolder; 

    public Drawing(ref ProgressBar pgbar, ref Panel panelBig) // Progressbar and panelBig as reference 
    { 
     this.panelHolder = panelBig; 
     this.progressBar = pgbar; 
     bgWorker = new BackgroundWorker(); 
     bgWorker.WorkerReportsProgress = true; 
     bgWorker.WorkerSupportsCancellation = true; 

     bgWorker.DoWork += new OpenNETCF.ComponentModel.DoWorkEventHandler(this.bgWorker_DoWork); 
     bgWorker.RunWorkerCompleted += new OpenNETCF.ComponentModel.RunWorkerCompletedEventHandler(this.bgWorker_RunWorkerCompleted); 
     bgWorker.ProgressChanged += new OpenNETCF.ComponentModel.ProgressChangedEventHandler(this.bgWorker_ProgressChanged); 
    } 

    public void createDrawing() 
    { 
     bgWorker.RunWorkerAsync(); 
    } 

    private void bgWorker_DoWork(object sender, DoWorkEventArgs e) 
    { 
     Panel panelContainer = new Panel(); 

      // Adding panels to the panelContainer 
      for(i=0; i<100; i++) 
      { 
      Panel panelSubpanel = new Panel(); 
      // Setting size, color, name etc.... 

      panelContainer.Controls.Add(panelSubpanel); // Adding the subpanel to the panelContainer 

      //Report the progress 
      bgWorker.ReportProgress(0, i); // Reporting number of panels loaded 
      } 

      e.Result = panelContainer; // Send the result(a panel with lots of subpanels) as an argument 
    } 

    private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) 
    { 
      this.progressBar.Value = (int)e.UserState; 
      this.progressBar.Update(); 
    } 

    private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     if (e.Error == null) 
     { 
      this.panelHolder   = (Panel)e.Result; 
     } 
     else 
     { 
      MessageBox.Show("An error occured, please try again"); 
     } 
    } 

} 

Instansiating的对象这个类：

public partial class Draw: Form 
{ 
    public Draw() 
    { 


     ProgressBar progressBarLoading = new ProgressBar(); 
     // Set lots of properties on progressBarLoading 

     Panel panelBigPanelContainer = new Panel();   

     Drawing drawer = new Drawing(ref progressBarLoading, ref panelBigPanelContainer); 

     drawer.createDrawing(); // this makes the object start a new thread, loading all the panels into a panel container, while also sending the progress to this progressbar. 
    } 

} 

这里是我的问题： 在私人无效bgWorker_RunWorkerCompleted（对象发件人，RunWorkerCompletedEventArgs E）

我没有得到e.Result，因为它应该是。 当我调试，并期待在e.Result，面板属性有此异常的消息：

'((System.Windows.Forms.Control)(e.Result)).ClientSize' threw an exception of type 'System.ObjectDisposedException' 

因此，对象被布置，但“为什么”是我的问题，我怎么能解决这个问题？

我希望有人会回答我，这让我疯狂。 我有另一个问题：是否允许使用带参数的“ref”？这是不好的编程？

在此先感谢。

我也写我如何理解下面的背景工人在这里：

---

这就是我认为是 “规则” 的背景工人：

bgWorker.RunWorkerAsync(); => starts a new thread. 
bgWorker_DoWork cannot reach the main thread without delegates 

-

private void bgWorker_DoWork(object sender, DoWorkEventArgs e) 
{ 
     // The work happens here, this is a thread that is not reachable by 
      the main thread 

     e.Result => This is an argument which can be reached by 
        bgWorker_RunWorkerCompleted() 


     bgWorker.ReportProgress(progressVar); => Reports the progress to the 
               bgWorker_ProgressChanged()   

} 

-

private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) 
    { 
      // I get the progress here, and can do stuff to the main thread from here 
       (e.g update a control) 

       this.ProgressBar.Value = e.ProgressPercentage; 
    } 

-

private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     // This is where the thread is completed. 
     // Here i can get e.Result from the bgWorker thread 
     // From here i can reach controls in my main thread, and use e.Result in my main thread 


     if (e.Error == null) 
     { 
      this.panelTileHolder = (Panel)e.Result; 

     } 
     else 
     { 
      MessageBox.Show("There was an error"); 
     } 
    } 

Answer 1

您在不同的线程创建UI控件（面板），并返回容器板回主线程。 UI控件具有线程关联。当后台工作完成时，它使用的线程被释放回线程池，并且在该进程中，与该线程相关联的UI控件显然被丢弃。稍后当您尝试在主线程中的RunWorkerCompleted事件处理程序中使用已放置的面板对象时，将得到ObjectDisposedException。

您需要在您的UI的主线程中创建这些面板。您可以在主线程中运行的ProgressChanged事件处理程序中创建它们，或者您可以调用另一种方法来检查InvokeRequired是否已启动，然后通过调用Invoke方法调用主线程上的操作。您可以隐藏这些面板，直到所有面板均已创建，并且在RunWorkerCompleted事件处理程序中可以显示它们。

我建议你看看下面的blogpost。

WinForms UI Thread Invokes: An In-Depth Review of Invoke/BeginInvoke/InvokeRequred

Answer 2

我跟不上你的代码，“imagePanel”似乎从天上掉下来的，没有它是怎么产生的任何概念。但是你所做的事情是非常非法的，Windows需要一个控件的Parent（由你的Controls.Add（）调用设置）成为一个窗口，该窗口与子代在同一个线程中创建。 .NET 2.0通常会检查这一点，并在违反该规则时生成IllegalOperationException，很难猜测为什么他们会将这些从CF中排除。如果他们实际上做到了。

当其RunWorkerCompleted或ProgressChanged事件运行并且表单已关闭时，ObjectDisposedException在BackgroundWorker中很常见。在您允许表单消失之前，您必须确保取消BGW。这在这里有点不相干，你必须彻底重新设计这个。