Encrypt The Messages

using System;
using System.Collections.Generic;   // needed for a List<T>
using System.Text;  // needed for a StringBuilder

class EncryptTheMessages
{
    static void Main()
    {
        string tempString = "";
        string inputString = "";
        int messageRows = -1;   // message counter
        List<string> arrayMessage = new List<string>(); // container for input message strings
        StringBuilder encryptedString = new StringBuilder();
        int[] specialSymbolsCodes1 = { 32, 44, 46, 63, 33 };    // array for special symbols 1
        int[] specialSymbolsCodes2 = { 43, 37, 38, 35, 36 };    // array for special symbols 2

        do
        {
            tempString = Console.ReadLine();    // temp string - before the real message lines
        }
        while ((tempString != "start") && (tempString != "START"));

        do
        {
            inputString = Console.ReadLine();   // real string - with message
            if (inputString != "")      // check for empty line
            {
                messageRows++;
                arrayMessage.Add(inputString);
            }
        }
        while ((inputString != "end") && (inputString != "END"));   // entering "end" will stop entering messages
        arrayMessage.RemoveAt(messageRows);     // remove the last iem in List: "end" word
        string[] stringArray = arrayMessage.ToArray();  //convert list to array with [messageRows] elements
        int asciiChar = 0;  // ascii code for a current char

        for (int i = 0; i < stringArray.Length; i++)    // loop for every line (message)
        {
            int lineLength = stringArray[i].Length;     // length of the stringArray at position [i]
            for (int j = lineLength - 1; j >= 0; j -- ) // reverse loop for stringArray[i] --> from length-1 to 0
            {
                char currentChar = Convert.ToChar(stringArray[i].Substring(j, 1));
                asciiChar = currentChar;        // get ascii code of currectchar

                // check ascii codes for a current char
                if (((asciiChar >= 65) && (asciiChar <= 77)) || ((asciiChar >= 97) && (asciiChar <= 109))) // letter [A...M]
                {
                    asciiChar += 13;
                }
                else if (((asciiChar >= 78) && (asciiChar <= 90)) || ((asciiChar >= 110) && (asciiChar <= 122)))  // [N...Z]
                {
                    asciiChar -= 13;
                }
                else
                {
                    for (int k = 0; k < specialSymbolsCodes1.Length; k ++)  // loop check special characters
                    {
                        if (asciiChar == specialSymbolsCodes1[k])
                        {
                            asciiChar = specialSymbolsCodes2[k];
                        }
                        else if (asciiChar == specialSymbolsCodes2[k])
                        {
                            asciiChar = specialSymbolsCodes1[k];
                        }
                    }
                }
                char tempChar = (char)asciiChar;
                encryptedString = encryptedString.Append(tempChar);
            }
            encryptedString = encryptedString.Append("\n");
        }
        if (messageRows > 0)
        {
            Console.WriteLine("Total number of messages: {0}", messageRows);
            Console.WriteLine(encryptedString.ToString());
            encryptedString.Clear();
        }
        else
        {
            Console.WriteLine("No message sent.");
        }

    }
}