26进制程序算法！十进制转换成26进制，26进制转换成十进制（次类可以直接调用C#）

public class Twenty_six_Sys
    {
        private static string[] Level = {"A", "B", "C", "D", "E", "F", "G",
    "H", "I", "G", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T",
    "U", "V", "W", "X", "Y", "Z" };
        /// <summary>
        /// 数字26进制，转换成字母，用递归算法
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>

        public static string Num_to_letter(int value)
        {
            //此处判断输入的是否是正确的数字，略（正在表达式判断）
            int remainder = value % 26;
            //remainder = (remainder == 0) ? 26 : remainder;
            int front = (value - remainder) / 26;
            if (front < 26)
            {
                return Level[front - 1] + Level[remainder];
            }
            else
            {
                return Num_to_letter(front) + Level[remainder];
            }
            //return "";
        }
        /// <summary>
        /// 26进制字母转换成数字
        /// </summary>
        /// <param name="letter"></param>
        /// <returns></returns>
        public static int Letter_to_num(string str)
        {
            //此处判断是否是由A-Z字母组成的字符串，略（正在表达式片段）
            char[] letter = str.ToCharArray(); //拆分字符串
            int reNum = 0;
            int power = 1; //用于次方算值
            int times = 1;  //最高位需要加1
            int num = letter.Length;//得到字符串个数
            //得到最后一个字母的尾数值
            reNum += Char_num(letter[num - 1]);
            //得到除最后一个字母的所以值,多于两位才执行这个函数
            if (num >= 2)
            {
                for (int i = num - 1; i > 0; i--)
                {
                    power = 1;//致1，用于下一次循环使用次方计算
                    for (int j = 0; j < i; j++)           //幂，j次方，应该有函数
                    {
                        power *= 26;
                    }
                    reNum += (power * (Char_num(letter[num - i - 1]) + times));  //最高位需要加1，中间位数不需要加一
                    times = 0;
                }
            }
            //Console.WriteLine(letter.Length);
            return reNum;
        }
        /// <summary>
        /// 输入字符得到相应的数字，这是最笨的方法，还可用ASIICK编码；
        /// </summary>
        /// <param name="ch"></param>
        /// <returns></returns>
        private static int Char_num(char ch)
        {
            switch (ch)
            {
                case 'A':
                    return 0;
                case 'B':
                    return 1;
                case 'C':
                    return 2;
                case 'D':
                    return 3;
                case 'E':
                    return 4;
                case 'F':
                    return 5;
                case 'G':
                    return 6;
                case 'H':
                    return 7;
                case 'I':
                    return 8;
                case 'J':
                    return 9;
                case 'K':
                    return 10;
                case 'L':
                    return 11;
                case 'M':
                    return 12;
                case 'N':
                    return 13;
                case 'O':
                    return 14;
                case 'P':
                    return 15;
                case 'Q':
                    return 16;
                case 'R':
                    return 17;
                case 'S':
                    return 18;
                case 'T':
                    return 19;
                case 'U':
                    return 20;
                case 'V':
                    return 21;
                case 'W':
                    return 22;
                case 'X':
                    return 23;
                case 'Y':
                    return 24;
                case 'Z':
                    return 25;

            }
            return -1;
        }
    }