using System;

using System.Threading;

using System.Threading.Tasks;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

​

int concurrency = 0;

Action action = new Action(() =>

{

    var current = Interlocked.Increment(ref concurrency);

    Console.WriteLine(@$"Started an action at {DateTime

        .Now:HH:mm:ss.fff} on thread #{Thread

        .CurrentThread.ManagedThreadId} with concurrency {current}");

    Thread.Sleep(1000);

    Interlocked.Decrement(ref concurrency);

});

Action[] actions = Enumerable.Repeat(action, 121).ToArray();

var options = new ParallelOptions() {  

    MaxDegreeOfParallelism = Environment.ProcessorCount *2 // default is -1

 };

Parallel.Invoke(options, actions);