Get a char from a binary number with 4 bits

getCharFromBinaryNumber4bits1.cs

/*
         * input is string of binary number, at most 4 bits "1100"
         */
        public static char getCharFromBinaryNumber(string s)
        {
            int sum = 0;

            foreach (char c in s)
            {
                int value = (c - '0');
                sum = value + sum * 2;
            }

            if (sum >= 0 && sum <= 9)
                return (char)(sum + '0');
            else
            {
                string charStr = "ABCDEF";
                char[] charArr = charStr.ToCharArray();

                return charArr[sum - 10];
            }
        }