using System;

using System.Linq;

using System.Threading;

using System.Threading.Tasks;

using System.Diagnostics;

​

class Program

{

    static void Main(string[] args)

    {

        TaskScheduler scheduler = new ConcurrentExclusiveSchedulerPair(

            TaskScheduler.Default, maxConcurrencyLevel: 3).ConcurrentScheduler;

​

        TaskFactory taskFactory = new TaskFactory(scheduler);

​

        Stopwatch stopwatch = Stopwatch.StartNew();

​

        Task[] tasks = Enumerable.Range(1, 12).Select(i => taskFactory.StartNew(async () =>

        {

            Thread.Sleep(500); // This counts towards the maxConcurrencyLevel

            Console.WriteLine($"Task: {i}, Elapsed: {stopwatch.Elapsed}");

            await Task.Delay(500); // This doesn't count towards the maxConcurrencyLevel

        }).Unwrap()).ToArray();

        Task.WaitAll(tasks);

    }

}

​