using System;

using System.Collections.Generic;

using System.Net;

using System.Net.NetworkInformation;

using System.Threading.Tasks;

using System.Threading.Tasks.Dataflow;

​

public class Program

{

    private static List<IPStatus> _results;

    public static async Task MyMethodAsync(IPAddress ip)

    {

        try

        {

            await Task.Delay(500);

            Console.WriteLine("here");

        }

        catch (Exception ex)

        {

        // note this is not thread safe best to lock it

        // _failed.Add(ip);

        }

    }

​

    public static async Task Asd()

    {

        var options = new ExecutionDataflowBlockOptions{MaxDegreeOfParallelism = 2};

        var block = new ActionBlock<IPAddress>(ip => MyMethodAsync(ip), options);

        var list = new List<IPAddress>{IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback, IPAddress.Loopback};

        foreach (var ip in list)

        {

            block.Post(ip);

        }

​

        Console.WriteLine("before");

        block.Complete();

        await block.Completion;

        Console.WriteLine("after");

    }

​

    public static void Main()

    {

         Asd().Wait();

        Console.WriteLine("asdsad");

    }

}