10进制转36进制

public static string C10_36(long i)
        {
            string s = "";
            int j = 0;
            while (i > 36)
            {
                j = i % 36;
                if (j < 10)
                    s += j.ToString();
                else
                    s += Convert.ToChar(j + 87);
                i = i \ 36;
            }
            if (i < 10)
                s += i.ToString();
            else
                s += Convert.ToChar(i + 87);
            Char[] c = s.ToCharArray();
            Array.Reverse(c);
            return new string(c);           
        }