BackgroundWorker不報告進度的問題

Question

我試圖使用後臺工作來顯示任務正在運行並向用戶報告當前進度。在我做了一般的搜索和嘗試簡單的例子之前，從未使用過背景工作。這是我目前陷入困境的地方。我在MSDN上使用這個例子：http://msdn.microsoft.com/en-us/library/cc221403(v=vs.95).aspx

但是，我試圖用webforms來做到這一點。所以我將頁面的Async屬性設置爲true。問題是它在整個過程中從不更新我的標籤。它只是在最後更新它。下面是代碼：

我創建了一個全球性的BackgroundWorker：

private BackgroundWorker bw = new BackgroundWorker(); 

在我的Page_Load方法，我有：

bw.WorkerReportsProgress = true; 
    bw.WorkerSupportsCancellation = false; 
    bw.DoWork += new DoWorkEventHandler(bw_DoWork); 
    bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged); 
    bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted); 

然後各種方法：

protected void btnSubmit_Click(object sender, EventArgs e) 
    { 
     if (!bw.IsBusy) bw.RunWorkerAsync(); 
    } 


    private void bw_DoWork(object sender, DoWorkEventArgs e) 
    { 
     BackgroundWorker worker = sender as BackgroundWorker; 

     for (int i = 1; i <= 10; i++) 
     { 
      System.Threading.Thread.Sleep(1000); 
      worker.ReportProgress(i * 10);    
     } 

    } 

    private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e) 
    { 
     lblProgress.Text = "Processing... " + e.ProgressPercentage.ToString() + "%"; 
    } 

    private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     if (e.Error != null) lblProgress.Text = "Error Updating: " + e.Error.Message; 
    } 

然而，它在整個過程中從不更新。我在10秒後看到處理... 100％。幫幫我？？

UPDATE

最終我能夠生成一個新的線程按照MSDN上的這個例子：http://msdn.microsoft.com/en-us/library/7a2f3ay4(v=vs.90).aspx

如果鏈接出現，以下是完整的示例代碼：

using System; 
using System.Threading; 

public class Worker 
{ 
    // This method will be called when the thread is started. 
    public void DoWork() 
    { 
     while (!_shouldStop) 
     { 
      Console.WriteLine("worker thread: working..."); 
     } 
     Console.WriteLine("worker thread: terminating gracefully."); 
    } 
    public void RequestStop() 
    { 
     _shouldStop = true; 
    } 
    // Volatile is used as hint to the compiler that this data 
    // member will be accessed by multiple threads. 
    private volatile bool _shouldStop; 
} 

public class WorkerThreadExample 
{ 
    static void Main() 
    { 
     // Create the thread object. This does not start the thread. 
     Worker workerObject = new Worker(); 
     Thread workerThread = new Thread(workerObject.DoWork); 

     // Start the worker thread. 
     workerThread.Start(); 
     Console.WriteLine("main thread: Starting worker thread..."); 

     // Loop until worker thread activates. 
     while (!workerThread.IsAlive); 

     // Put the main thread to sleep for 1 millisecond to 
     // allow the worker thread to do some work: 
     Thread.Sleep(1); 

     // Request that the worker thread stop itself: 
     workerObject.RequestStop(); 

     // Use the Join method to block the current thread 
     // until the object's thread terminates. 
     workerThread.Join(); 
     Console.WriteLine("main thread: Worker thread has terminated."); 
    } 
} 

Answer 1

您不能以這種方式從ASP.NET頁面報告進度。

你需要一些傳輸機制來做到這一點。一些選項：

1. 使用AJAX輪詢每X秒的進度;
2. 使用Web套接字將進度報告回客戶端。