while (true) {

                Console.WriteLine("请输入学生姓名");

                string a = Console.ReadLine();

                if (a == "q") {

                    Console.WriteLine("结束");

                    break;

                }

            }

  Console.WriteLine("请输入学生姓名");

                string a = Console.ReadLine();

                while (a != "q") {

                    Console.WriteLine("请输入学生姓名");

                    a = Console.ReadLine();

                }

                Console.WriteLine("请按任意键退出");

                Console.ReadKey();