Problem with Task synchronization

Question

I'm having a problem getting task synchronization to work.  In the following test program, the first 5 second delay never happens and the detail field is not cleared before the second sleep (the dialog just immediately shows the stage of 3 and the incremented value of 500 and then waits the 3 seconds and then hides the dialog.  Any ideas what i'm doing wrong here?  Thanks!

	public partial class MainWindow : Window
	{
		private ProgressDlg dlgProgress;
		private int ProgressCount = 0;

		public MainWindow()
		{
			InitializeComponent();
		}

		static int rcnt = 0;
		private void OnClickTest(object sender, RoutedEventArgs e)
		{
			++rcnt;
			string strTest = "Testing LeftDir" + rcnt.ToString();
			LWDMSettings.Instance.LeftDir = strTest;
			strTest = "Testing RightDir" + rcnt.ToString();
			LWDMSettings.Instance.RightDir = strTest;
			LWDMSettings.Instance.ProgressStage = "Showing the progress stage";
			LWDMSettings.Instance.ProgressDetails = "";
			dlgProgress.Show();
			Task.Factory.StartNew(() =>
			{
				TestTask1();
			});
		}

		private void OnLoaded(object sender, RoutedEventArgs e)
		{
			dlgProgress = new ProgressDlg();
			dlgProgress.Owner = this;
		}

		private void TestTask1()
		{
			ProgressCount = 0;
			LWDMSettings.Instance.ProgressStage = "Beginning TestTasks2";
			LWDMSettings.Instance.ProgressDetails = "";
			List<Task> tasks = new List<Task>();
			var t = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t);
			t = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t);
			Task.Factory.ContinueWhenAll(tasks.ToArray(),
				   result0 =>
				   {
					   Thread.Sleep(5000);
				   });
			tasks.Clear();
			LWDMSettings.Instance.ProgressStage = "Beginning TestTasks3";
			LWDMSettings.Instance.ProgressDetails = "";
			t = Task.Factory.StartNew(() =>
			{
				TestTask3();
			});
			tasks.Add(t);
			t = Task.Factory.StartNew(() =>
			{
				TestTask3();
			});
			tasks.Add(t);
			Task.Factory.ContinueWhenAll(tasks.ToArray(),
				   result1 =>
				   {
					   Thread.Sleep(3000);
					   this.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
					   {
						   dlgProgress.Hide();
					   }));
				   });
		}

		private void TestTask2()
		{
			for (int i = 0; i < 250; i++)
			{
				Interlocked.Increment(ref ProgressCount);
				if (ProgressCount % 50 == 0)
				{
					LWDMSettings.Instance.ProgressDetails = String.Format("Incremented value is {0}", ProgressCount);
				}
			}
		}

		private void TestTask3()
		{
		}
	}

Answer 1

Hiya

 

I may be mistaken, but the first thing I notice is you're reusing the t object, when you should be creating a new one.

 

			var t = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t);
			t = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t);

 

I think this should be:

 

 

			var t = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t);
			var t2 = Task.Factory.StartNew(() =>
			{
				TestTask2();
			});
			tasks.Add(t2);

 

There may be something else but I don't have time right now to recreate your example.

 

Best regards,
Pedro

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Answer 2

Okay, I made those changes but it still doesn't work.  I could zip up my project if there were a way to post/send it to you?

Answer 3

I think I see my problem.  I was looking at the ContinueWhenAll as similar to the MFC WaitForAll which would block until all the ResetEvents were set.  I see now that I need to nest the next tasks within the ContinueWhenAll, etc.  I'd be more comfortable if there were a WaitForAllTasksToComplete but I can't seem to find anything like that in Tasks.  Is there such a thing?  Thanks!

Answer 4

Hi lwdaddio,

If you could try to use Task.WaitAll() method

http://msdn.microsoft.com/en-us/library/dd270695.aspx

 

Best regards,

---

Sheldon _Xiao[MSFT]
MSDN Community Support | Feedback to us
Microsoft
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