using System;

using System.IO;

using System.IO.Compression;

using System.Threading.Tasks;

using System.Threading;

​

public class Program

{

    public static void Main()

    {

        Task.Run(async () =>

        {

            try

            {

                var sampleData = new byte[ 35000 ];

                Console.WriteLine( "With GZipStream, WriteAsync NOT called" );

                // Normally would use a file like this

                // using (var fs = new System.IO.FileStream(@"C:\BTR\Source\Assemblies\BTR.Rbl.Evolution.Documents.dll", 

                //      System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.None, 8192, true))

                using( var fs = new MemoryStream( sampleData ) )

                using (var ss = new GZipStream(new SampleStream(), CompressionMode.Compress))

                {

                    await fs.CopyToAsync(ss);

                }

                Console.WriteLine( "Without GZipStream, WriteAsync *correctly* called" );

                using( var fs = new MemoryStream( sampleData ) )

                using (var ss = new SampleStream())

                {

                    await fs.CopyToAsync(ss);

                }

                Console.WriteLine( "Complete" );

            }

            catch ( Exception ex )

            {

                Console.WriteLine( ex.Message );

            }

        }).Wait();

    }

}

​

public class SampleStream : System.IO.Stream

{

    public override bool CanRead { get { return true; } }

    public override bool CanSeek { get { return false; } }

    public override bool CanWrite { get { return true; } }

​

    public override long Seek(long offset, SeekOrigin origin)

    {

        throw new NotImplementedException();

    }

    public override long Length

    {

        get { throw new NotImplementedException(); }

    }

    public override void SetLength(long value)

    {

        throw new NotImplementedException();

    }

​

    public override long Position

    {

        get { throw new NotImplementedException(); }

        set { throw new NotImplementedException(); }

    }

​

    public override void Flush() { Console.WriteLine( "Flush" ); }

​

    public override int Read(byte[] buffer, int offset, int count)

    {

        Console.WriteLine( "Read" );

        return 0;

    }

    public override void Write(byte[] buffer, int offset, int count) { Console.WriteLine( "Write" ); }

​

    public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)

    {

        if (!cancellationToken.IsCancellationRequested)

        {

            Console.WriteLine("ReadAsync");

            return Task.FromResult( 0 );

        }

​

        return Task.FromResult( 0 );

    }

​

    public async override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)

    {

        Console.WriteLine("WriteAsync");

        await Task.Delay( 1 );

    }

}

​