private static byte[] GZipUncompress(byte[] data)
{
    using(var input = new MemoryStream(data))
    using(var gzip = new GZipStream(input, CompressionMode.Decompress))
    using(var output = new MemoryStream())
    {
        gzip.CopyTo(output);
        return output.ToArray();
    }
}

private static byte[] GZipCompress(byte[] data)
{
    using(var input = new MemoryStream(data))
    using (var output = new MemoryStream())
    {
        using (var gzip = new GZipStream(output, CompressionMode.Compress, true))
        {
            input.CopyTo(gzip);
        }
        return output.ToArray();
    }
}