using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading;

using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

        var parallelOptions = new ParallelOptions()

        {

            MaxDegreeOfParallelism = 3,

            TaskScheduler = new ThreadPerTask_TaskScheduler()

        };

        Parallel.ForEach(Enumerable.Range(1, 10), parallelOptions, item =>

        {

            Console.WriteLine($"{DateTime.Now:HH:mm:ss.fff}" +

                $" [{Thread.CurrentThread.ManagedThreadId}]" +

                $" Processing #{item}" +

                (Thread.CurrentThread.IsBackground ? ", Background" : "") +

                (Thread.CurrentThread.IsThreadPoolThread ? ", ThreadPool" : ""));

            Thread.Sleep(500); // Simulate CPU-bound work

        });

    }

​

    public class ThreadPerTask_TaskScheduler : TaskScheduler

    {

        protected override void QueueTask(Task task)

        {

            var thread = new Thread(() => TryExecuteTask(task));

            thread.IsBackground = true;

            thread.Start();

        }

​

        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)

        {

            return TryExecuteTask(task);

        }

​

        protected override IEnumerable<Task> GetScheduledTasks() { yield break; }

    }

}