using System;

using System.Diagnostics;

using System.IO;

using System.Linq;

using System.Net;

using System.Text;

using System.Threading.Tasks;

​

namespace Parallel

{

    public enum Actions

    {

        TestParallelDownload,

        TestParallelSaveFile,

        TestAsyncDownload,

        TestAsyncSaveFile

    }

​

    public class Program

    {

        public static async Task Main(string[] args)

        {

            try

            {

                var stopWatch = Stopwatch.StartNew();

                var itemAmount = 5;

​

                await Test(Actions.TestParallelDownload, itemAmount);

                await Test(Actions.TestParallelSaveFile, itemAmount);

​

                await Test(Actions.TestAsyncDownload, itemAmount);

                await Test(Actions.TestAsyncSaveFile, itemAmount);

​

                stopWatch.Stop();

                Console.WriteLine("Finish {0}", stopWatch.Elapsed);

                Console.ReadLine();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Err", ex.Message);

                Console.ReadLine();

            }

        }

​

        public static async Task Test(Actions action, int itemAmount)

        {

            string[] items = Enumerable.Range(0, itemAmount).Select(i => Guid.NewGuid().ToString()).ToArray();

            var stopWatch = Stopwatch.StartNew();

​

            switch (action)

            {

                case Actions.TestParallelDownload:

                    items.AsParallel().ForAll(item => DownloadAsync(item));

                    break;

                case Actions.TestParallelSaveFile:

                    items.AsParallel().ForAll(item => SaveAsync(item));

                    break;

                case Actions.TestAsyncDownload:

                    foreach (var item in items)

                        await DownloadAsync(item);

                    break;

                case Actions.TestAsyncSaveFile:

                    foreach (var item in items)

                        await SaveAsync(item);

                    break;

            }

​

            stopWatch.Stop();

​

            Console.WriteLine($"{action.ToString()} Call: Time: {stopWatch.Elapsed}");

        }

​

        public static async Task SaveAsync(string textToWrite)

        {

            string filePath = @"C:\temp\file2.txt";

            byte[] encodedText = Encoding.Unicode.GetBytes(textToWrite);

​

            using (var sourceStream = new FileStream(filePath,

                FileMode.Append, FileAccess.Write, FileShare.None,

                bufferSize: 4096, useAsync: true))

            {

                await sourceStream.WriteAsync(encodedText, 0, encodedText.Length);

            };

        }

​

        public static async Task DownloadAsync(string name)

        {

            var uri = new Uri("https://images.sftcdn.net/images/t_app-logo-l,f_auto,dpr_auto/p/ce2ece60-9b32-11e6-95ab-00163ed833e7/2183169552/the-test-fun-for-friends-logo.png");

            using (var client = new WebClient())

            {

                await client.DownloadFileTaskAsync(uri, $"{name}.png");

            }

        }

    }

}

​