VS 复习，if...else if..else 和if..else的嵌套学习

 static void Main666(string[] args)
        {
            Console.WriteLine("输入分数：");

          string fs = Console.ReadLine();
            int score = Convert.ToInt32(fs);

            if (score < 60)
            {
                Console.WriteLine("是否认真做作业？(是，否)");

                string zuoye = Console.ReadLine();

                #region ======加分=======
                if (zuoye == "是")
                {
                    score = score + 5;

                    if (score < 60)
                    {
                        Console.WriteLine("不及格");
                    }
                    else
                    {
                        Console.WriteLine("凑合及格");
                    }
                }
                else
                {
                    Console.WriteLine("不及格了");
                }
                #endregion
            }
            else
            {

            }

            Console.WriteLine("结束");
        }

        static void Main222(string[] args)
        {
            Console.WriteLine("输入分数：");

            string fs = Console.ReadLine();
            int score = Convert.ToInt32(fs);

            #region  判断分数
            if (score >= 0 && score < 60)
            {
                Console.WriteLine("不及格，补考");
            }
            else if (score >= 60 && score < 80)
            {
                Console.WriteLine("恭喜及格");
            }
            else if (score >= 80 && score <= 100)
            {
                Console.WriteLine("恭喜优秀");
            }
            else
            {
                Console.WriteLine("输入有误");
            }
            #endregion
            
            Console.WriteLine("结束");
        }

        static void Main111(string[] args)
        {
            int a = 10;
            int b = 5;
            int c = (a++) + b;
            int d = (++a) + b;

            Console.WriteLine(a);
            Console.WriteLine(c);
            Console.WriteLine(d);
        }
        static void abc(string[] args)
        {
            Console.WriteLine("输入分数：");
            
            string fs = Console.ReadLine();
            int score = Convert.ToInt32(fs);

            if (score < 60)
            {
                Console.WriteLine("不及格，需要补考");
            }

            Console.WriteLine("结束");
        }