Running tasks in sequence inside an infinite loop [closed]

问题

I have a several tasks that are run in sequence; one after the other.

Task.Factory.StartNew(() => DoWork1())
            .ContinueWith((t1) => DoWork2())
            .ContinueWith(t2 => DoWork3());

I want to put this inside a loop so they run indefinitely (After DoWork3() is done, go back to DoWork1(). I tried putting inside a while loop, but the loop goes to the next iteration as soon the task is launched, creating a boatload of new tasks.

Would also be nice to have a way to exit condition to break out of the loop, maybe pass a cancellation token.

Thanks!

回答1:

The simplest way would be to use async/await:

async void DoStuff()
{
    while (true)
    {
        await Task.Factory.StartNew(() => DoWork1())
            .ContinueWith((t1) => DoWork2())
            .ContinueWith(t2 => DoWork3());
    }
}

Or you can call the method again after the last task is completed, simulating a while(true) :

void DoStuff()
{
    Task.Factory.StartNew(() => DoWork1())
        .ContinueWith((t1) => DoWork2())
        .ContinueWith(t2 => DoWork3())
        .ContinueWith(t3=> DoStuff());
}

You could also Wait for the task explicitly, but this will block the thread you are executing on:

void DoStuff()
{
    while (true)
    {
        Task.Factory.StartNew(() => DoWork1())
            .ContinueWith((t1) => DoWork2())
            .ContinueWith(t2 => DoWork3())
            .Wait();
    }
}

回答2:

You can wait for the task to complete before starting the next iteration of while loop.

while(true) 
{
    var task = Task.Factory.StartNew(() => DoWork1())
            .ContinueWith((t1) => DoWork2())
            .ContinueWith(t2 => DoWork3());
    task.Wait(); 
}

Without task.Wait() (or a similar mechanism) the tasks will be scheduled to run, but the next iteration of while loop will begin without waiting for these tasks to complete.

回答3:

You can do something as follows:

List<Task> tasks = new List<Task>();

for (int i = 0; i < 10; i++) //your loop
{
    var task = Task.Factory.StartNew(() => DoWork1()).ContinueWith((t1) => DoWork2()).ContinueWith(t2 => DoWork3());
    tasks.Add(task);
}

Task.WaitAll(tasks.ToArray());

来源：https://stackoverflow.com/questions/49043126/running-tasks-in-sequence-inside-an-infinite-loop

标签

multithreading

task

task-parallel-library