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   1: ThreadPool.QueueUserWorkItem(new WaitCallback(Job), parameter);

   1:  

   2:  

   3:  

   4: private void Job(object path)

   5: {

   6:    //重設統計數據 

   7:    fileCount = 0;

   8:    totalSize = 0;

   9:    //統計檔案數及大小 

  10:    explore(path.ToString());

  11:  

  12:    //顯示結果 (跨執行緒)

  13:    string text = $"{fileCount} files, {totalSize} bytes";

  14:    

  15:    //透過Invoke，強制以UI Thread執行

  16:    this.Invoke(

  17:        new UpdateLabelHandler(printResult),

  18:        new object[] { text });  

  19: }

  20: //宣告一個delegate

  21: delegate void UpdateLabelHandler(string text);

  22: //透過Invoke，printReulst會以UI Thread執行 

  23: //故可隨意存取UI Control

  24: private void printResult(string text)

  25: {

  26:    lblResult.Text = text;

  27: }

   1: private void runBtn_Click(object sender, EventArgs e)

   2: {

   3:     if(runBtn.Text == "Run")

   4:     {

   5:         runBtn.Text = "Cancel";

   6:         lblResult.Text = string.Empty;

   7:  

   8:         fileCount = 0;

   9:         totalSize = 0;

  10:         backgroundWorker1.RunWorkerAsync(txtPath.Text);

  11:     }

  12:     else

  13:     {

  14:         //設定取消旗標 

  15:         backgroundWorker1.CancelAsync();

  16:         //cancel = true; 

  17:         

  18:         //在完全停止前，停用按鈕 

  19:         runBtn.Enabled = false; 

  20:  

  21:     }

  22:  

  23: }

   1: private void explortFolderJob(string path, BackgroundWorker worker)

   2: {

   3:     //使用遞迴搜索所有目錄 

   4:     foreach (string dir in Directory.GetDirectories(path))

   5:     {                

   6:         //使用者要求中止 

   7:         if (worker.CancellationPending) return;

   8:         explortFolderJob(dir, worker);

   9:     }

  10:  

  11:     foreach (string file in Directory.GetFiles(path))

  12:     {

  13:         //使用者要求中止 

  14:         if (worker.CancellationPending) return;

  15:  

  16:         Interlocked.Increment(ref fileCount);

  17:  

  18:         //每100個檔案回報一下進度

  19:         if(fileCount%100==0)

  20:         {

  21:             this.Invoke(

  22:                 new UpdateLabelHandler(updateProgress),

  23:                  $"{fileCount} files"

  24:             );

  25:         }

  26:  

  27:         //fileCount++;

  28:         //加總檔案大小 

  29:         FileInfo fi = new FileInfo(file);

  30:         totalSize += fi.Length;

  31:     }

  32: }

   1: private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)

   2: {

   3:    explortFolderJob((string)e.Argument, sender as BackgroundWorker);

   4:    //執行完成，設執行定結果 

   5:    if (backgroundWorker1.CancellationPending)

   6:        e.Cancel = true;

   7:    else

   8:        e.Result = $"{fileCount} files, {totalSize} bytes";

   9: }

  10:  

  11: private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)

  12: {

  13:    lblResult.Text = e.UserState.ToString();

  14: }

  15:  

  16: private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

  17: {

  18:    lblResult.Text = (e.Cancelled) ? "Canceled" : //取消

  19:        e.Result.ToString();                     // 結果

  20:    runBtn.Text = "Run";

  21:    runBtn.Enabled = true;

  22: }