System.Text.RegularExpressions.RegexParser.ScanControl C# (CSharp) Method

        internal char ScanControl()
        {
            char ch;

            if (CharsRight() <= 0)
                throw MakeException(SR.MissingControl);

            ch = MoveRightGetChar();

            // \ca interpreted as \cA

            if (ch >= 'a' && ch <= 'z')
                ch = (char)(ch - ('a' - 'A'));

            if ((ch = (char)(ch - '@')) < ' ')
                return ch;

            throw MakeException(SR.UnrecognizedControl);
        }