求1-100的和&&.输入一个数n，打印1-n出来&&求1-100以内所有偶数的和

           int b = 0;
            for (int i = 1; i <=100; i++)
            {
                b = b+i; 
            }
            Console.WriteLine("1-100的和b为：" + b);    

            Console.WriteLine("请输入一个数n:");
            int n = int.Parse(Console.ReadLine());
            for (int i = 1; i <= n; i++)
            {
                Console.WriteLine(i); 
            }

           int sum = 0;
            for (int i = 0; i <=100; i=i+2)
            {
                sum += i;
            }
            Console.WriteLine(sum);