c#使用ROT13加密，解密

ROT13是一种简单的加密方式，主要是把26个英文字母前13个和后13个对调，起到一定的英文文字加密保护作用。

虽然加密方式简单，但是Windows的注册表里面都使用了ROT13加密，可见其使用还是比较多的。

public string ROT13Encode(string InputText)
        {
            int i;
            char CurrentCharacter;
            int CurrentCharacterCode;
            string EncodedText = "";

            //Iterate through the length of the input parameter 
            for (i = 0; i < InputText.Length; i++)
            {
                //Convert the current character to a char 
                CurrentCharacter = System.Convert.ToChar(InputText.Substring(i, 1));

                //Get the character code of the current character 
                CurrentCharacterCode = (int)CurrentCharacter;
                //Modify the character code of the character, - this 
                //so that "a" becomes "n", "z" becomes "m", "N" becomes "Y" and so on 
                if (CurrentCharacterCode >= 97 && CurrentCharacterCode <= 109)
                {
                    CurrentCharacterCode = CurrentCharacterCode + 13;
                }
                else if (CurrentCharacterCode >= 110 && CurrentCharacterCode <= 122)
                {
                    CurrentCharacterCode = CurrentCharacterCode - 13;
                }
                else if (CurrentCharacterCode >= 65 && CurrentCharacterCode <= 77)
                {
                    CurrentCharacterCode = CurrentCharacterCode + 13;
                }
                else if (CurrentCharacterCode >= 78 && CurrentCharacterCode <= 90)
                {
                    CurrentCharacterCode = CurrentCharacterCode - 13;
                }

                //Add the current character to the string to be returned 
                EncodedText = EncodedText + (char)CurrentCharacterCode;
            }

            return EncodedText;

        } 

加密和解密的方法都一样，把字符串传入方法返回得到的字符串就是要加密和解密的字符串了。