EncryptTheMessages

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

namespace EncryptTheMessages
{
    class EncryptTheMessages
    {
        static void Main()
        {
            string inputMessages = Console.ReadLine();
            int counterOfMessages = 0;
            List<string> messages = new List<string>();
            while (inputMessages.ToUpper() != "START")
            {
                inputMessages = Console.ReadLine();
            }
            inputMessages = Console.ReadLine();
            while (inputMessages != "END" && inputMessages != "end")
            {
                if (inputMessages != "" && inputMessages != "END" && inputMessages != "end")
                {
                    counterOfMessages++;
                    messages.Add( inputMessages );
                }
                inputMessages = Console.ReadLine();
            }
            if (counterOfMessages > 0)
            {
                Console.WriteLine( "Total number of messages: {0}" , counterOfMessages );
                for (int i = 0; i < messages.Count; i++)
                {
                    EncryptMessages( messages[i] );
                }
            }
            else
            {
                Console.WriteLine( "No messages sent." );
            }
        }
        private static void EncryptMessages( string inputMessages )
        {
            string outputMessages = string.Empty;
            foreach (char item in inputMessages)
            {
                if (char.IsLetter( item ))
                {
                    if (item >= 65 && item <= 77 || item >= 97 && item <= 109)
                    {
                        outputMessages += ( char )( item + 13 );
                    }
                    else
                    {
                        if (item <= 90 && item > 77 || item > 109 && item <= 122)
                        {
                            outputMessages += ( char )( item - 13 );
                        }
                    }
                }
                else
                {
                    switch (item)
                    {
                        case ' ': outputMessages += ( char )( item + 11 ); break;
                        case ',': outputMessages += ( char )( item - 7 ); break;
                        case '.': outputMessages += ( char )( item - 8 ); break;
                        case '?': outputMessages += ( char )( item - 28 ); break;
                        case '!': outputMessages += ( char )( item + 3 ); break;
                        default: outputMessages += ( char )item; break;
                    }
                }
            }
            outputMessages = new string( outputMessages.ToCharArray().Reverse().ToArray() );
            Console.WriteLine( outputMessages );
        }
    }
}