C#中通过类来继承两个接口，父类实例化接口中的方法，子类继承父类，调用方法

实现了父类继承接口，父类实例化接口的方法，子类继承父类，子类调用父类的方法直接使用

代码如下：

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

namespace sortAndArea
{

    public interface Sort
    {
          List<int> sort();
    }

    public interface Area
    {
        long area();
    }

     abstract  class CoustomMath : Sort, Area
    {
         public CoustomMath()
         {
          // public  List<int> list = new List<int> { };
         }

        public List<int> list = new List<int> {  };     //使用泛型
        public  int l = ;

        public List<int> sort()
        {
            l = list.Count;
            int temp = ;
            //Console.WriteLine(l);
            for (int i = ; i < l ; i++)         //排序
            {
                for (int j = i+; j < l; j++)
                {
                    if (list[i] > list[j])
                    {
                        temp = list[i];
                        list[i] = list[j];
                        list[j] = temp;
                    }
                }
            }
            return list;
        }

        public long area()
        {
            long sum = ;
            for (int k = ; k < l; k++)
            {
                sum += list[k];
            }
            long r = sum;
            long area =(long) Math.PI * r * r;    //求面积

            return area;
        }  

    }

     class Program : CoustomMath
    {
         public List<int> list = new List<int> { };

         public Program()
         {
             list = new List<int> { , , , , , ,  };
             base.list = list;

         }

         //Program pp = new Program();
         static void Main(string[] args)
         {
              //List<int>  list = new List<int> {  };

             Program pp = new Program();
             Console.WriteLine("从小到大的排序为：");
             pp.sort();
             int l1 = ;
             l1 = pp.l;
             for (int i=;i<l1;i++)
             {
                 Console.Write(pp.list[i]+" ");
             }
             Console.WriteLine("\n");
             Console.WriteLine("求和之后的面积为：");
             Console.WriteLine(pp.area());
             Console.ReadKey();
         }

    }

}