函数（方法）

 class hanshu
    {
        public void qiuhe(int n)
        {
            int sum = 0;
            for (int i = 0; i <= n; i++)
            {
                sum += i;

            }
            Console.Write("求和结果为"+sum);
        }
        static void Main(string[] args)
        {
            hanshu hs = new hanshu();
            Console.Write("输入数字：");
            int n = int.Parse(Console.ReadLine());
            hs.qiuhe(n);
            Console.ReadLine();
        }
    }

class Program
    {
        public string fanhuinihao()
        {
            return "你好";
        }
        static void Main(string[] args)
        {
            Program fh=new Program();
            string s = fh.fanhuinihao();
            Console.Write(s);
            Console.ReadLine();
        }
    }