How to manage a list of tasks using the Task Parallel Library

Question

I'm trying to manage a list of tasks for a Windows Service so when I shut down the Service, I can use the Task.WaitAll() method to stop the Service from shutting down until all of the remaining tasks complete. For example, I have a Run() method that executes until a boolean is updated:

public void Run()
{
    while (runFlag)
    {
        if (MaxTasksAchieved)
        {
            System.Threading.Thread.Sleep(pollingInterval);
        }
        else
        {

            taskList.Add(Task.Factory.StartNew(() =>
            {
                // do stuff
            }));
        }
    }
}

Then in my Stop() method, I have the following:

public void Stop()
{
    runFlag = false;

    if (taskList.Count > 0)
    {
        // wait
        Task.WaitAll(taskList.ToArray());
    }
    else
    {
        // no wait, great.
    }
}

My question is how do I elegantly have the task remove itself from the list after it's done executing? I want the task to remove itself from the list so when Stop() is called, taskList only contains the tasks that are currently in progress.

Answer 1

If you want to remove the task from the list simply add a continuation that does that:

taskList.Add(task.ContinueWith(t = > taskList.Remove(t)));

But you can simply use Task.WaitAll on all the tasks since the completed tasks are already completed.

Task.WaitAll(taskList.ToArray());

You can easily wait only on the running tasks by filtering the list with the tasks status

Task.WaitAll(taskList.Where(t => t.Status != TaskStatus.RanToCompletion).ToArray());