C#

/// <summary>
/// G-ZIP (.gz) Decompression method.  Places new file in the same folder.
/// </summary>
/// <see cref="http://msdn2.microsoft.com/en-us/library/system.io.compression.gzipstream.aspx"/>
/// <param name="file">File to be decompressed.</param>
private static void gDecompress(FileInfo file)
{
    // Get the stream of the source file.
    using (FileStream inFile = file.OpenRead())
    {
        // Get original file extension, for example "doc" from report.doc.gz.
        string curFile = file.FullName;
        string origName = curFile.Remove(curFile.Length - file.Extension.Length);

        //Create the decompressed file.
        using (FileStream outFile = File.Create(origName))
        {
            using (GZipStream Decompress = new GZipStream(inFile, CompressionMode.Decompress))
            {
                //Copy the decompression stream into the output file.
                byte[] buffer = new byte[4096];
                int numRead;
                while ((numRead = Decompress.Read(buffer, 0, buffer.Length)) != 0)
                {
                    outFile.Write(buffer, 0, numRead);
                }
            }
        }
    }
}