C# ascii碼與字符的轉換

using System;
using System.Text;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("輸入要轉為ascii碼的字符");
            string a = Console.ReadLine();  //接收字符串
            try
            {
                Console.WriteLine(Asc(a));  //將字符串轉為ascii碼並打印
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
            Console.WriteLine("輸入要轉為字符的ascii碼");
            string b = Console.ReadLine();  //接收ascii碼
            try
            {
                Console.WriteLine(Cha(b));  //將ascii碼字符串轉為並打印
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }

        /*字符轉ascii碼*/
        private static int Asc(string s)
        {
            if (s.Length == 1)
            {
                ASCIIEncoding a = new ASCIIEncoding();
                int b = (int)a.GetBytes(s)[0];  //利用ASCIIEncoding類的GetByte()方法轉碼
                return b;
            }
            else
            {
                throw new Exception("String is not vaild");
            }
        }

        /*ascii碼轉字符*/
        private static char Cha(string s)
        {
            int a = int.Parse(s);   //現將字符串轉成int類型
            if (a >= 0 && a <= 255)     //若不在這個范圍內，則不是字符
            {
                char c = (char)a;   //利用類型強轉得到字符
                return c;
            }
            else
            {
                throw new Exception("String is not vaild");
            }
        }
    }
}