Guid

        static void Main(string[] args)
        {
            for(int i = 0; i < 100; i++)
            {
                Console.WriteLine(GuidResult("N"));
                Console.WriteLine(GuidResult("D"));
                Console.WriteLine(GuidResult("B"));
                Console.WriteLine(GuidResult("P"));
                Console.WriteLine(GuidResult("X"));
                Console.WriteLine(i.ToString());
            }
            Console.ReadLine();
        }

        public static string GuidResult(string s)
        {
            return Guid.NewGuid().ToString($"{s}").ToUpper();
        }

 主要用于做数据库的主键，唯一标识符