using System.IO;
using System.IO.Compression;
public class Program {
   public static void Main() {
      string sFileIn = @"C:\Test.txt";
      string sFileOut = @"C:\Test.bin";
      byte[] content = File.ReadAllBytes(sFileIn);
      FileStream fileStream = new FileStream( sFileOut, 
                                     FileMode.Create, FileAccess.Write);
      GZipStream gzipStream = new GZipStream( fileStream, 
                                     CompressionMode.Compress );
      gzipStream.Write(content, 0, content.Length);
      gzipStream.Close();
      fileStream.Close();
      FileInfo fileOut = new FileInfo(sFileOut);
      System.Console.WriteLine("{0} bytes before", content.Length);
      System.Console.WriteLine("{0} bytes after", fileOut.Length);
   }
}