PrepareZip.cs

private void PrepareZip(string filePath)
{
    FileInfo gZipfile = new FileInfo(filePath);
    FileInfo gzipFileName = new FileInfo(string.Concat(gZipfile.FullName, ".gz"));
    using (FileStream fileToBeZippedAsStream = gZipfile.OpenRead())
    {
        using (FileStream gzipTargetAsStream = gzipFileName.Create())
        {
            using (GZipStream gzipStream = new GZipStream(gzipTargetAsStream, CompressionMode.Compress))
            {
                try
                {
                    fileToBeZippedAsStream.CopyTo(gzipStream);
                }
                catch (Exception ex) { throw ex; }
            }
        }
    }
}