System.Net.WebUtility.IsUrlSafeChar C# (CSharp) Method

        private static bool IsUrlSafeChar(char ch)
        {
            // Set of safe chars, from RFC 1738.4 minus '+'
            /*
            if (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z' || ch >= '0' && ch <= '9')
                return true;

            switch (ch)
            {
                case '-':
                case '_':
                case '.':
                case '!':
                case '*':
                case '(':
                case ')':
                    return true;
            }

            return false;
            */
            // Optimized version of the above:

            int code = (int)ch;

            const int safeSpecialCharMask = 0x03FF0000 | // 0..9
                1 << ((int)'!' - 0x20) | // 0x21
                1 << ((int)'(' - 0x20) | // 0x28
                1 << ((int)')' - 0x20) | // 0x29
                1 << ((int)'*' - 0x20) | // 0x2A
                1 << ((int)'-' - 0x20) | // 0x2D
                1 << ((int)'.' - 0x20); // 0x2E

            return ((uint)(code - 'a') <= (uint)('z' - 'a')) ||
                   ((uint)(code - 'A') <= (uint)('Z' - 'A')) ||
                   ((uint)(code - 0x20) <= (uint)('9' - 0x20) && ((1 << (code - 0x20)) & safeSpecialCharMask) != 0) ||
                   (code == (int)'_');
        }