public List<List<char>> Results(List<char> allValues)
        {
            var collection = new List<List<char>>();
            for (int counter = 0; counter < (1 << allValues.Count); ++counter)
            {
                List<char> combination = new List<char>();
                for (int i = 0; i < allValues.Count; ++i)
                {
                    if ((counter & (1 << i)) == 0)
                        combination.Add(allValues[i]);
                }

                // do something with combination
                collection.Add(combination);
            }
            return collection;
        }

        void PowerSetofChars()
        {
            var chars = new List<char> { 'A', 'B', 'C' };

            var result = Results(chars);

        }