使用任务和异常处理进行多线程处理

Question

I have an application created in C# .Net 4.5. I am using multithreading via the task class. I want to add some error handling. Specifically I want any exception to bubble up to the top of my application.

Where I am stuck is how unhandled exceptions or any for that matter work whilst using tasks.

I have been reading this page http://msdn.microsoft.com/en-us/library/dd997415(v=vs.110).aspx . My understanding is that if I have multiple tasks running and error happens that I have to wait until the Task.WaitAll(someTask) is called and can handle it there - is that correct? Is it possible when an error happens on one task to cancel all the other tasks before having to wait for Task.WaitAll(someTask)?

Below is a snippet of my code. I guess with nested tasks the same principle applies that I would have to wait until after both Task.WAitAll()'s have been called before handling my error? My approach for this application is rather simple, any execption thrown I want to be logged and then close the application. Just not sure how this works with tasks.

Also is it correct the way I am creating two TaskFactory's? Both methods are in different classes.

public void RunTimePeriods()
        {
            _taskFactory = new TaskFactory();

            Task[] taskTimePeriod = new Task[_timePeriods.Length];

            for (int i = 0; i < taskTimePeriod.Length; i++)
                taskTimePeriod[i] = _taskFactory.StartNew(_timePeriods[i].RunIndicators);

            Task.WaitAll(taskTimePeriod);
         }


public void RunIndicators()
        {
            _taskFactory = new TaskFactory();

            Task[] taskIndicator = new Task[_indicator.Length];

            for (int i = 0; i < taskIndicator.Length; i++)
                taskIndicator[i] = _taskFactory.StartNew(_indicator[i].Run);
        }

Answer 1

Is it possible when an error happens on one task to cancel all the other tasks before having to wait for Task.WaitAll(someTask)?

The only way you can do this is to notify the other tasks to stop what they are doing. The general solution for this type of communication is to use task cancellation .

Here's a good walkthrough .