caesar.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace iziprogzh4
{
    internal class Program
    {
        internal static string Caesar(string value, int shift, bool Encrypt = true)
        {
            char[] buffer = value.ToCharArray();
            for (int i = 0; i < buffer.Length; i++)
            {
                char letter = buffer[i];
                if (Encrypt) letter = (char)(letter + shift);
                else letter = (char)(letter - shift);
                if (letter > 'z')
                {
                    letter = (char)(letter - 26);
                }
                else if (letter < 'a')
                {
                    letter = (char)(letter + 26);
                }
                buffer[i] = letter;
             }
             return new string(buffer);
         }

         internal static void Main()
         {
	        string a = "test";
	        string b = Caesar(a, 18);
	        string c = Caesar(b, -18); 

	        string d = Caesar(a, 1);
	        string e = Caesar(d, -1);

	        string f = "exxegoexsrgi";
	        string g = Caesar(f, -4);

	        Console.WriteLine(a);
	        Console.WriteLine(b);
	        Console.WriteLine(c);
	        Console.WriteLine(d);
	        Console.WriteLine(e);
	        Console.WriteLine(f);
	        Console.WriteLine(g);

            Console.WriteLine(Caesar("buzi", 1));
            Console.WriteLine(Caesar("cvaj", 1, false));
            Console.ReadKey();
          }
    }
}