using System;

using System.Linq;

using System.Threading.Tasks;

using Nito.AsyncEx;

​

public class Program

{

    public static void Main()

    {

        AsyncContext.Run(async () =>

        {

            ParallelOptions options = new()

            {

                MaxDegreeOfParallelism = 2,

                TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext()

            };

​

            textBox1.AppendText(@$"MaxDegreeOfParallelism: {options

                .MaxDegreeOfParallelism}, MaximumConcurrencyLevel: {options

                .TaskScheduler.MaximumConcurrencyLevel}" + "\r\n\r\n");

​

            await Parallel.ForEachAsync(Enumerable.Range(1, 5), options, async (x, _) =>

            {

                textBox1.AppendText($"Processing #{x}\r\n");

                await Task.Delay(200); // Simulate an I/O-bound operation.

                textBox1.AppendText($"Completed #{x}\r\n");

            });

        });

    }

​

    private static class textBox1 // Simulate updating the UI of a WinForms app.

    {

        public static void AppendText(string text) => Console.Write(text);

    }

}

​