Question

public static Int64 Decode(string input)
        {
            var reversed = input.ToLower().Reverse();
            long result = 0;
            int pos = 0;
            foreach (char c in reversed)
            {
                result += CharList.IndexOf(c) * (long)Math.Pow(36, pos);
                pos++;
            }
            return result;
        }

I am using a method to decode a value from base36 to decimal. The method works fine
but when I get to decode the input value of “000A” then things start to go wrong and it
decodes this as -1.

Can anyone see what’s going wrong? I am really confused with the code and how it works.

private const string CharList = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

Answer 1

You’re using ToLower() on your source and your list contains uppercase chars only, so IndexOf('a') returns -1.

I think you’d want to use ToUpper() instead.