public enum CompressionMethod
{
    GZip = 1,
    Deflate = 2
}

public class CompressedContent : HttpContent
{
    private readonly HttpContent _originalContent;
    private readonly CompressionMethod _compressionMethod;

    public CompressedContent(HttpContent content, CompressionMethod compressionMethod)
    {
        if (content == null)
        {
            throw new ArgumentNullException("content");
        }

        _originalContent = content;
        _compressionMethod = compressionMethod;

        foreach (KeyValuePair<string, IEnumerable<string>> header in _originalContent.Headers)
        {
            Headers.TryAddWithoutValidation(header.Key, header.Value);
        }

        Headers.ContentEncoding.Add(_compressionMethod.ToString().ToLowerInvariant());
    }

    protected override bool TryComputeLength(out long length)
    {
        length = -1;
        return false;
    }

    protected async override Task SerializeToStreamAsync(Stream stream, TransportContext context)
    {
        if (_compressionMethod == CompressionMethod.GZip)
        {
            using (var gzipStream = new GZipStream(stream, CompressionMode.Compress, leaveOpen: true))
            {
                await _originalContent.CopyToAsync(gzipStream);
            }
        }
        else if (_compressionMethod == CompressionMethod.Deflate)
        {
            using (var deflateStream = new DeflateStream(stream, CompressionMode.Compress, leaveOpen: true))
            {
                await _originalContent.CopyToAsync(deflateStream);
            }
        }
    }
}