BASE64 encoder/decoder

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace base64cd
{
    //BASE64 encoder/decoder
    class Program
    {
        static void PrintHelp()
        {
            string EXEName = Path.GetFileName (System.Reflection.Assembly.GetExecutingAssembly().CodeBase);

            Console.WriteLine("BASE64 encoder/decoder");
            Console.WriteLine("Use:");
            Console.WriteLine(EXEName+" <-c|-d> <filename1> [filename2] [filename3] ... ");
            Console.WriteLine("-c - Encode to BASE64");
            Console.WriteLine("-d - Decode from BASE64");
            Console.WriteLine("filenameN - File name or file mask (*.txt, *.*, etc...)");
        }


        static void Main(string[] args)
        {
            string dir = "";
            if (args.Length < 2)
            {
                PrintHelp();
                return;
            };

            switch (args[0])
            {
                case "-c":
                    {
                        dir = Directory.GetCurrentDirectory(); //Current dir

                        for (int i = 1; i < args.Length; i++)
                        {

                            string[] files = Directory.GetFiles(dir,
                                args[i], SearchOption.TopDirectoryOnly); //find files

                            if (files.Length < 1)
                            {
                                Console.WriteLine(args[i] + " not found");
                            }
                            else
                            {
                                foreach (string f in files)
                                {
                                    Console.Write(f+": ");

                                    try
                                    {
                                        byte[] buf = File.ReadAllBytes(f);
                                        File.Copy(f, f + ".bak", true);
                                        string B64Str = Convert.ToBase64String(buf);
                                        File.WriteAllText(f, B64Str);
                                        Console.WriteLine("OK");
                                    }
                                    catch (Exception ex)
                                    {
                                        Console.WriteLine("ERROR " + ex.Message);
                                    }
                                }
                            }
                        }
                    }; break;
                case "-d":
                    {
                        dir = Directory.GetCurrentDirectory(); //Current dir

                        for (int i = 1; i < args.Length; i++)
                        {

                            string[] files = Directory.GetFiles(dir,
                                args[i], SearchOption.TopDirectoryOnly); //find files

                            if (files.Length < 1)
                            {
                                Console.WriteLine(args[i] + " not found");
                            }
                            else
                            {
                                foreach (string f in files)
                                {
                                    Console.Write(f + ": ");

                                    try
                                    {
                                        string B64Str = File.ReadAllText(f);
                                        File.Copy(f, f + ".bak", true);
                                        byte[] buf = Convert.FromBase64String(B64Str);
                                        File.WriteAllBytes(f, buf);
                                        Console.WriteLine("OK");
                                    }
                                    catch (Exception ex)
                                    {
                                        Console.WriteLine("ERROR " + ex.Message);
                                    }
                                }
                            }
                        }
                    };break;
                default:
                    {
                        PrintHelp();
                        return;
                    }
            }

        }
    }
}