C#凯撒加密

using System;
namespace ConsoleApplication3
{
class Program
{
static int AscII(string str)
{
byte[] array = new byte[1];
array = System.Text.Encoding.ASCII.GetBytes(str);
int asciicode = (short)(array[0]);
return asciicode;
}
static void Main(string[] args)
{
int key;
string strCaesar = "";
string str = " ";
char[] ch = new char[10000];
Console.WriteLine("请输入秘钥字符：");
key = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("请连续输入原文)：");
str = Console.ReadLine();
Console.WriteLine("请依次输入原文字母)：");
for (int i = 0; i < str.Length; i++)
{
ch[i] = Convert.ToChar(Console.ReadLine());
string sou = ch[i].ToString();
string tar = "";
bool isChar = "abcdefghijklmnopqrstuvwxyz".Contains(sou.ToLower());
bool isToUpperChar = isChar && (sou.ToUpper() == sou);
sou = sou.ToLower();
if (isChar)
{
int offset = (AscII(sou) + key - AscII("a")) % (AscII("z") - AscII("a") + 1);
tar = Convert.ToChar(offset + AscII("a")).ToString();
if(isUpperChar)
{
tar = tar.ToUpper();
}
}
else
{
tar = sou;
}
strCaesar += tar;
}
Console.WriteLine("秘钥key为：{0}", key);
Console.WriteLine("凯撒加密前原文为：{0}", str);
Console.WriteLine("凯撒加密后密文为：{0}", strCaesar);
}
}
}。