能帮我看下这个编码，给我解释下么？

            int num1 = 50;//声明常量
            Console.WriteLine("num1++={0}",num1++);
            Console.WriteLine("num1={0}",num1);
            num1 = 50;
            Console.WriteLine("++num1={0}",++num1);

            int num2 = 40;//声明常量
            Console.WriteLine("num2-={0}",num2--
                );
            Console.WriteLine("-num2={0}",-num2);