using System.IO;

using System.IO.Compression;

string sourceFile=@"C:\1.txt";

string destinationFile=@"D:\2.zip";

        private const long BUFFER_SIZE = 20480;

       if ( File.Exists ( sourceFile ))

       {

            FileStream sourceStream = null;

            FileStream destinationStream = null;

            GZipStream compressedStream = null;

            try

            {

                // Read the bytes from the source file into a byte array

                sourceStream = new FileStream ( sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read );

 

                // Open the FileStream to write to

                destinationStream = new FileStream ( destinationFile, FileMode.OpenOrCreate, FileAccess.Write );

 

                // Create a compression stream pointing to the destiantion stream

                compressedStream = new DeflateStream ( destinationStream, CompressionMode.Compress, true );

            long bufferSize = sourceStream.Length < BUFFER_SIZE ? sourceStream.Length : BUFFER_SIZE;  

            byte[] buffer = new byte[bufferSize];  

            int bytesRead = 0;  

            long bytesWritten = 0;  

            while ((bytesRead = sourceStream.Read(buffer, 0, buffer.Length)) != 0)  

            {  

                compressedStream.Write(buffer, 0, bytesRead);  

                bytesWritten += bufferSize;  

            }  

 

            }

            catch ( ApplicationException ex )

            {

                Console.WriteLine(ex.Message);

            }

            finally

            {

                // Make sure we allways close all streams

                if ( sourceStream != null )

                    sourceStream.Close ( );

 

                if ( compressedStream != null )

                    compressedStream.Close ( );

 

                if ( destinationStream != null )

                    destinationStream.Close ( );

            }

        }