using System;

using System.Collections.Generic;

using System.Net;

using System.Net.NetworkInformation;

using System.Threading;   

​

static class Icmp

{

    static Disposable<List<Ping>> PingAll(List<Tuple<IPAddress,string>> a, Action<List<string>> completion)

    {

        List<string> results = new List<string>();

        List<Ping> pings = new List<Ping>();

        int doneCount = 0;

        Action done = () => { if (doneCount >= a.Count) completion(results); };

        foreach (var item in a)

        {

            var p = new Ping();

            pings.Add(p);

            p.PingCompleted += (o, e) => {

                results.Add(item.Item2);

                Interlocked.Increment(ref doneCount);

                done();

            };

            try

            {

                p.SendAsync(item.Item1, 1000);

            }

            catch

            {

                Interlocked.Increment(ref doneCount);

                done();

            }

        }

        return Disposable.AsDisposable(pings, () => pings.ForEach(p => p.Dispose()));

    }

}