C# Online Compiler | .NET Fiddle

<no name> by Anonymous

using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

static class Program
{
    static void Main()
    {
        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, 12).ToArray();
        var options = new ParallelOptions() { MaxDegreeOfParallelism = -1 };
        Parallel.Invoke(options, actions);
    }
}

​x
 
using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
​
static class Program
{
    static void Main()
    {
        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, 12).ToArray();
        var options = new ParallelOptions() { MaxDegreeOfParallelism = -1 };
        Parallel.Invoke(options, actions);
    }
}

Started an action at 17:28:33.138 on thread #6 with concurrency 2
Started an action at 17:28:33.138 on thread #8 with concurrency 4
Started an action at 17:28:33.138 on thread #7 with concurrency 3
Started an action at 17:28:33.138 on thread #4 with concurrency 1
Started an action at 17:28:33.138 on thread #1 with concurrency 5
Started an action at 17:28:34.139 on thread #9 with concurrency 6
Started an action at 17:28:34.157 on thread #6 with concurrency 6
Started an action at 17:28:34.158 on thread #7 with concurrency 6
Started an action at 17:28:34.158 on thread #1 with concurrency 6
Started an action at 17:28:34.158 on thread #4 with concurrency 6
Started an action at 17:28:34.158 on thread #8 with concurrency 6
Started an action at 17:28:35.139 on thread #9 with concurrency 6

Cached Result
Last Run:	5:28:33 pm
Compile:	0.02s
Execute:	3.06s
Memory:	6.59Mb
CPU:	3.08s

View IL Code