using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace sx8_1
{
    interface Ijia
    { void jia();}

    interface Ijian
    { void jian();}

    class jisuan : Ijia, Ijian
    {
        public int a;
        public int b;

        public jisuan(int A, int B)
        { a = A; b = B; }
        public void jia()
        { return a + b; }

    }

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入第一个数：");
            int m = int.Parse(Console.ReadLine());

            Console.WriteLine("请输入第二个数：");
            int n = int.Parse(Console.ReadLine());

            ji suan js = new jia(m, n);
            Console.ReadLine("两数之和是：{0}", jia());
            jisuan js = new jian(m, n);

            
                Console.ReadLine("两数之差是：{0}", jia());
                Console.ReadLine();
            
        }



    }
}

看来这个太  不好搞了  哎……自己琢磨吧！这C#基础有啥难的？老子得搞定他哎…………

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace sx8_1
{
    interface Ijia
    {

        int jia();
    }

    interface Ijian
    {

        int jian();
    }

    class jisuan : Ijia, Ijian
    {
        public int a;
        public int b;

        public jisuan(int A, int B)
        {

            a = A; b = B;
        }
        public int jia()
        {

            return a + b;

        }
        public int jian()
        {

            return a - b;

        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入第一个数：");
            int m = int.Parse(Console.ReadLine());

            Console.WriteLine("请输入第二个数：");
            int n = int.Parse(Console.ReadLine());

            jisuan js = new jisuan(m, n);

            Console.WriteLine("两数之和是：{0}", js.jia());
            Console.WriteLine("两数之差是：{0}", js.jian());

            /*以下代码让程序暂停*/
            Console.WriteLine("按任意键退出......\n");
            Console.ReadLine();
        }
    }
}

太感谢了，真是帮了大忙了！

楼上编译好清晰

Console.WriteLine("请输入两个数");
            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());
            int[] num = { a, b };
            double jia = 0; double jian = num[0];
            for (int i = 0; i < 2; i++)
            {
                jia += num[i];               
            }
            for (int i = 0; i < 1; i++)
            {
                jian -= num[1];               
            }
            Console.WriteLine("两数之和{0}",jia);
            Console.WriteLine("两数只差{0}",jian);
同样的cshare，为什么我只会这样写？