how to ZIP file on hard disk.

Read the file we are going to compress into a FileStream

string filename = Server.MapPath("aatish.txt");
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();