compress.cs

using System;
using System.IO;
using System.Text.RegularExpressions;
using System.IO.Compression;

namespace Compression
{
    class MyCompression
    {
        static string removeExt(string str) {
            Regex rgx = new Regex(@"\.\w+$");
            
            return  rgx.Replace(str, "");
        }

        static bool isCompressed(string filename) {
            int last = filename.Length;
            string ext = filename.Substring(last - 3, 3);

            if (ext == ".gz") return true;
            else return false;
        }

        static void Compress(string filePath) {
            string arhivePath = filePath + ".gz";

            GZipStream compStream = new GZipStream( File.Create(arhivePath) , CompressionMode.Compress); 
            FileStream file = new FileStream(filePath, FileMode.Open);
                
            int theByte = file.ReadByte();

            while ( theByte != -1) {
                compStream.WriteByte(Convert.ToByte(theByte));
                theByte = file.ReadByte();
            }

            compStream.Dispose();  
            file.Close();
        }

        static void Uncompress(string arhivePath) {
            string filename = removeExt(arhivePath);
            
            GZipStream arhive = new GZipStream( File.Create(arhivePath) , CompressionMode.Decompress); 
            FileStream uncompressedFile = new FileStream(filename, FileMode.Open);
                
            int theByte = arhive.ReadByte();

            while ( theByte != -1) {
                uncompressedFile.WriteByte(Convert.ToByte(theByte));
                theByte = arhive.ReadByte();

            }

            uncompressedFile.Close();
            arhive.Dispose(); 
            arhive.Close(); 
        } 

        static void Main(string[] args) {
            string file;


            if (args.Length < 1) {
                Console.WriteLine("no argument passed.\n Use compress.exe pathToSourceFile");
            } else {
                file = args[0];

                if (isCompressed(file)) {
                    Uncompress(file);
                } else {
                    Compress(file);
                }
   
            }
        }
    }
}