怎么判断一个字符串中包含几个字母,几个数字,几个标点

            string s = "abcd45612,asd";
            int characters = 0;
            int numbers = 0;
            int symbols = 0;
            foreach (char c in s)
            {
                if ((c >= 33 && c <= 47) || (c >= 58 && c <= 64) || (c >= 91 && c <= 96) || (c >= 123 && c <= 126))
                    symbols++;
                if ((c >= 65 && c <= 90) || (c >= 97 && c <= 122))
                    characters++;
                if (c >= 48 && c <= 57)
                    numbers++;
            }
            Console.WriteLine("共有{0}个字母，{1}个数字，{2}个标点", characters, numbers, symbols);