using System;

using System.Linq;

using System.Threading.Tasks;

using System.Net;

using System.Collections.Generic;

using System.Collections.Concurrent;

public class Program

{

    public static void Main()

    {

        var urls = new[] { "http://www.google.co.uk", "http://www.microsoft.com" };

        Attempt1b(urls);

    }

    // Kicks off all requests sequentially, but handles the responses in parallel

    private static void Attempt1(string[] urls)

    {

        var tasks = urls.Select(async url =>

        {

            var webClient = new WebClient();

            var result = await webClient.DownloadStringTaskAsync(url);

            // Process the result

            return result;

        }).ToList();

        while (tasks.Count > 0)

        {

            var index = Task.WaitAny(tasks.ToArray());

            var result = tasks[index].Result;

            Console.WriteLine(result.Length);

            tasks.RemoveAt(index);

        }

    }

    private static void Attempt1b(string[] urls)

    {

        var tasks = urls.Select(url =>

        {

            var webClient = new WebClient();

            var task = webClient.DownloadStringTaskAsync(url)

                .ContinueWith(t =>

            {

                // Process the result

                return t.Result;

            });

            return task;

        }).ToList();

        while (tasks.Count > 0)

        {

            var index = Task.WaitAny(tasks.ToArray());

            var result = tasks[index].Result;

            Console.WriteLine(result.Length);

            tasks.RemoveAt(index);

        }

    }

    // Batches requests in parallel, and handles responses in parallel

    private static void Attempt2(string[] urls)

    {

        var tasks = urls.AsParallel().Select(url => Task.Run(async () =>

        {

            var webClient = new WebClient();

            var result = await webClient.DownloadStringTaskAsync(url);

            // Process the result

            return result;

        })).ToList();

        while (tasks.Count > 0)

        {

            var index = Task.WaitAny(tasks.ToArray());

            var result = tasks[index].Result;

            Console.WriteLine(result.Length);

            tasks.RemoveAt(index);

        }

    }

}