Question

我已经读了2个小时，我仍然感到困惑。有人说使用StartNew，有人说Task.Run有人说别的。我知道Task.Run给了我一个编译错误。

我需要并行启动多个任务，然后当每个任务成功完成时执行延续任务。知道什么时候完成阻止会有所帮助。

这就是我所拥有的：

    public void DoSomeWork(object workItem)
    {
        var tasks = new Task<ResultArgs>[_itemList.Count];

        for (int loopCnt = 0; loopCnt < _itemList.Count; loopCnt++)
        {
            tasks[loopCnt] = new Task<ResultArgs>.Run(() =>
            {
                return _itemList[loopCnt].Analyze(workItem);
            });
            tasks[loopCnt].ContinueWith(ReportResults, TaskContinuationOptions.ExecuteSynchronously);
        }
    }

编译说任务中不存在运行。

显然，我有一些运行但我不知道是什么。

我如何解决这个问题？

Answer 1

您可以使用async方法，也可以将项目转换为数据流，以下代码使用Tpl-dataflow处理您的项目，将其传递到第二个处理步骤，最后等待处理完成

using NUnit.Framework;
using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;

namespace AsyncProcessing {

    [TestFixture]
    public class PipelineTests {

        [Test]
        public async Task RunPipeline() {
            var pipeline = new MyPipeline();
            var data = Enumerable.Range(0, 1000).Select(x => new WorkItem(x, x));

            foreach(var item in data) {
                await pipeline.SendAsync(item);
            }

            pipeline.Complete();
            await pipeline.Completion;

            //all processing complete            
        }
    }

    class MyPipeline {

        private BufferBlock<WorkItem> inputBuffer;
        private TransformBlock<WorkItem, WorkItem> analyzeBlock;
        private TransformBlock<WorkItem, ResultArg> reportBlock;
        private ActionBlock<ResultArg> postOutput;

        public ConcurrentBag<ResultArg> OutputBuffer { get; }
        public Task Completion { get { return postOutput.Completion; } }

        public MyPipeline() {
            OutputBuffer = new ConcurrentBag<ResultArg>();
            CreatePipeline();
            LinkPipeline();
        }

        public void Complete() {
            inputBuffer.Complete();
        }

        public async Task SendAsync(WorkItem data) {
            await inputBuffer.SendAsync(data);
        }

        public void CreatePipeline() {
            var options = new ExecutionDataflowBlockOptions() {
                MaxDegreeOfParallelism = Environment.ProcessorCount,
                BoundedCapacity = 10
            };

            inputBuffer = new BufferBlock<WorkItem>(options);

            analyzeBlock = new TransformBlock<WorkItem, WorkItem>(item => {
                //Anylyze item....
                return item;
            }, options);

            reportBlock = new TransformBlock<WorkItem, ResultArg>(item => {
                //report your results, email.. db... etc.
                return new ResultArg(item.JobId, item.WorkValue);
            }, options);

            postOutput = new ActionBlock<ResultArg>(item => {
                OutputBuffer.Add(item);
            }, options);
        }

        public void LinkPipeline() {
            var options = new DataflowLinkOptions() {
                PropagateCompletion = true,
            };

            inputBuffer.LinkTo(analyzeBlock, options);
            analyzeBlock.LinkTo(reportBlock, options);
            reportBlock.LinkTo(postOutput, options);
        }
    }

    public class WorkItem {

        public int JobId { get; set; }
        public int WorkValue { get; set; }

        public WorkItem(int id, int workValue) {
            this.JobId = id;
            this.WorkValue = workValue;
        }
    }

    public class ResultArg {

        public int JobId { get; set; }
        public int Result { get; set; }

        public ResultArg(int id, int result) {
            this.JobId = id;
            this.Result = result;
        }
    }
}

Answer 2

为什么不使用Parallel.ForEach循环。这用于并行执行任务，它可以使用多个线程，执行速度更快 Parallet.Foreach

但是，如果您正在进行涉及锁定的数据库相关输入输出操作，则可能会失败。在这种情况下，我建议在每个任务中保留一个返回类型，并根据前一个任务的返回类型启用ext任务。

具有连续性的简单并行任务

2 个答案: