how i can compress files with minimize size by .net

// Read the file we are going to compress into a FileStream
            string filename = Program.x;

            FileStream infile = File.OpenRead(filename);
            byte[] buffer = new byte[infile.Length];
            infile.Read(buffer, 0, buffer.Length);
            infile.Close();

            // Create the output file
            FileStream outfile = File.Create(Path.ChangeExtension(filename, "zip"));

            // Compress the input stream and write it to the output FileStream
            GZipStream gzipStream = new GZipStream(outfile, CompressionMode.Compress);
            gzipStream.Write(buffer, 0, buffer.Length);
            gzipStream.Close();