最佳实践LongRunning任务创建 [英] Best Practice LongRunning Task creation

问题描述

这是一个很好的设计，需要使用任务API在.NET 4.0中运行一个后台线程？我唯一​​担心的是，如果我们要取消这项任务我会怎么做呢？我知道我可以只设置 ProgramEnding 到真，但我知道有一个的CancellationToken 任务的API中。

Is this a good design for a background thread that needs to be run using the Task API in .Net 4? My only concern is if we want to cancel that task how I would do it? I know I can just set ProgramEnding to true but I know there is a CancellationToken in the Task API.

这是code只是一个例子样品，这样一个线程将被添加到集合而另一个线程会从它删除。任务是设置为LongRunning，因为这需要连续运行，而在程序运行

This is just an example sample of code so that one thread will be adding to a collection and another thread will be removing from it. The Task is setup as LongRunning as this needs to be running continuously whilst the program is running

private void RemoveFromBlockingCollection()
{
    while (!ProgramEnding)
    {
       foreach (var x in DataInQueue.GetConsumingEnumerable())
       {
          Console.WriteLine("Task={0}, obj={1}, Thread={2}"
                          , Task.CurrentId, x + " Removed"
                          , Thread.CurrentThread.ManagedThreadId);
       }
    }
}

private void button1_Click(object sender, EventArgs e)
{
   DataInQueue = new BlockingCollection<string>();
   var t9 = Task.Factory.StartNew(RemoveFromBlockingCollection
                                 , TaskCreationOptions.LongRunning);

   for (int i = 0; i < 100; i++)
   {
     DataInQueue.Add(i.ToString());
     Console.WriteLine("Task={0}, obj={1}, Thread={2}", 
                       Task.CurrentId, i + " Added", 
                       Thread.CurrentThread.ManagedThreadId);
     Thread.Sleep(100);
   }
   ProgramEnding = true;
}

更新：我发现，我可以删除ProgramEnding布尔和使用DataInQueue.CompleteAdding这由此带来的线程结束

UPDATE: I have found that I can remove the ProgramEnding boolean and use DataInQueue.CompleteAdding which which bring the thread to an end.

推荐答案

正如你已经提到的，你可以使用的CancellationToken。做这种方式：

As you already mentioned, you can use the CancellationToken. Do it this way:

var cancellationTokenSource = new CancellationTokenSource();
Task.Factory.StartNew(RemoveFromBlockingCollection
                      , TaskCreationOptions.LongRunning
                      , cancellationTokenSource.Token);  

在你随后的code，你可以取消任务：

And later in your code, you can cancel the task with:

cancellationTokenSource.Cancel();

在您的长时间运行的任务，你可以问的道理，如果有人要求取消：

In your long running task you can ask the token, if cancellation was requested:

if (cancellationTokenSource.Token.IsCancellationRequested)

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