using System;

using System.IO;

using System.Collections.Generic;

using System.Diagnostics;

using System.Text;

​

public class Program

{

static async System.Threading.Tasks.Task Main()

{

    // Run each one so JIT startup doesn't affect timing

    CreateArchiveSync();

    CreateArchiveAsync().Wait();

    // Start timing

    var swSync = System.Diagnostics.Stopwatch.StartNew();

    var syncHash = CreateArchiveSync();

    swSync.Stop();

    var swAsync = System.Diagnostics.Stopwatch.StartNew();

    var asyncHash = await CreateArchiveAsync();

    swAsync.Stop();

​

    if (syncHash != asyncHash)

    {

        throw new Exception("HASH MISMATCH");

    }

    System.Console.WriteLine("Sync: " + swSync.ElapsedMilliseconds);

    System.Console.WriteLine("Async: " + swAsync.ElapsedMilliseconds);

}

​

private static async System.Threading.Tasks.Task<string> CreateArchiveAsync()

{

    using (var stream = new System.IO.MemoryStream())

    {

        using (var archive = new System.IO.Compression.ZipArchive(stream, System.IO.Compression.ZipArchiveMode.Update, true))

        {

            var lstTask = new System.Collections.Generic.List<System.Threading.Tasks.Task>();

            // We want to ensure concurrency, so we have a delay in CreateEntryAsync set to i.  We're stepping backwards, so the first item 

            // will delay 50 ms, next item will delay 49ms, etc.

            for (int i = 50; i >= 0; i--) 

            {

                lstTask.Add(CreateEntryAsync(archive, i));

            }

            await System.Threading.Tasks.Task.WhenAll(lstTask);

        }

        return SHA256Hash(stream);

    }

}

​

private static string CreateArchiveSync()

{

    using (var stream = new System.IO.MemoryStream())

    {

        using (var archive = new System.IO.Compression.ZipArchive(stream, System.IO.Compression.ZipArchiveMode.Update, true))

        {

            for (int i = 50; i >= 0; i--)

            {

                CreateEntryAsync(archive, i).Wait();

            }

        }

        return SHA256Hash(stream);

    }

}

​

private static async System.Threading.Tasks.Task CreateEntryAsync(System.IO.Compression.ZipArchive archive, int i) 

{

    var entry = archive.CreateEntry(System.Guid.NewGuid().ToString() + i + ".txt");

    using (var entryStream = entry.Open())

    {

        await System.Threading.Tasks.Task.Delay(i); // Simulate larger write

        var t = Encoding.UTF8.GetBytes("Test" + i);

        await entryStream.WriteAsync(t, 0, t.Length);

        //System.Console.WriteLine("Zipped " + i);

    }

}

​

private static string SHA256Hash(Stream stream)

{

    using (var s = new BufferedStream(stream, 1200000))

    {

        var sha = new System.Security.Cryptography.SHA256Managed();

        byte[] checksum = sha.ComputeHash(s);

        return BitConverter.ToString(checksum).Replace("-", String.Empty);

    }

}

}