问题描述
我需要执行 n BackgroundWorkers,当他们完成时,我想引发一个事件,并根据他们的所有工作来做些事情。我的用例是创建队列,填充队列,然后仅运行一次。为此,我制作了一个ParallelQueue类。经过最初的测试,它似乎可以正常工作,但是我担心条件_max == _iteration
并不是最好的条件,那就是评估队列中的所有工作是否已经完成。还是我对Queue的使用不是线程安全的,我应该使用什么来完成此任务? (ConcurrentQueue?)如果这个问题太笼统,我将其删除,谢谢。
public class ParallelQueue
{
private Queue<BackgroundWorker> _queue;
private readonly object _key = new object();
private int _max = 0;
private int _iteration = 0;
private bool _ran = false;
public ParallelQueue()
{
_queue = new Queue<BackgroundWorker>();
}
public delegate void BackgroundQueueCompleted(object sender,RunWorkerCompletedEventArgs e);
public event BackgroundQueueCompleted QueueCompleted;
public void Add(BackgroundWorker worker)
{
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(WorkerCompleted);
_queue.Enqueue(worker);
}
public void Run()
{
lock (_key)
{
if(!_queue.Any()) throw new ArgumentOutOfRangeException("ParallelQueue cannot be empty");
if (_ran) throw new InvalidOperationException("ParallelQueue can only be run once");
_ran = true;
_max = _queue.Count();
Parallel.For(0,_queue.Count,(i,state) =>
{
BackgroundWorker worker = _queue.Dequeue();
worker.RunWorkerAsync();
});
}
}
private void WorkerCompleted(object sender,RunWorkerCompletedEventArgs e)
{
Interlocked.Increment(ref _iteration);
if (_max == _iteration)
{
QueueCompleted?.Invoke(this,e);
}
}
}
使用ParallelQueue的示例
public class Program
{
static void Main(string[] args)
{
var queue = new ParallelQueue();
queue.QueueCompleted += MyQueueCompletedHandler;
for (int i = 0; i < 10; i++)
{
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += new DoWorkEventHandler((sender,e) =>
{
Thread.Sleep(500);
});
queue.Add(bw);
}
queue.Run();
Console.ReadLine();
}
private static void MyQueueCompletedHandler(object sender,RunWorkerCompletedEventArgs e)
{
Console.WriteLine("queue is complete");
}
}
解决方法
在Task Parallel Library(TPL)于2010年推出之后,BackgroundWorker
类实际上已过时。如果您要做的工作结果是同质的,则可以使用{{ 3}}方法,或者,如果您熟悉LINQ,请使用Parallel.ForEach
。这是一个PLINQ示例:
var input = new List<int>() { 1,2,3,4,5,6,7,8,9,10 };
int[] results = input
.AsParallel()
.AsOrdered() // optional
.WithDegreeOfParallelism(2) // optional
.Select(x => { Thread.Sleep(500); return x * 2; }) // simulate some work
.ToArray();
如果结果不同,则可以为每个工作创建一个PLINQ,将其存储在List<Task>
中,等待所有任务,然后通过Task<TResult>
获取结果每个属性。示例:
var task1 = Task.Run(() => { Thread.Sleep(500); return 1; });
var task2 = Task.Run(() => { Thread.Sleep(500); return "Helen"; });
var task3 = Task.Run(() => { Thread.Sleep(500); return DateTime.Now; });
var list = new List<Task>() { task1,task2,task3 };
Task.WaitAll(list.ToArray());
int result1 = task1.Result;
string result2 = task2.Result;
DateTime result3 = task3.Result;