C# 练习

第一单元

1.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace _17._9._18
{

 class Program
    {
        static void Main(string[] args)
        {
            Console.Write("请输入一个整数：");
            int n = int.Parse(Console.ReadLine());
            int sum=0;
            if(n%2!=0)
            {
                for(int i=1;i<=n;i++)
                {
                    if (i % 2 != 0)
                        sum += i;
                }
                Console.Write("该数及比该数小的所有奇数之和为：");
                Console.WriteLine(sum);
                Console.Read();
            }
            else
            {
                for (int j = 2; j <= n; j++)
                {
                    if (j % 2 == 0)
                        sum += j;
                }
                Console.Write("该数及比该数小的所有偶数之和为；");
                Console.WriteLine(sum);
                Console.Read();
               
            }
        }
    }
}

11.

第二单元

1.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Animal
{
    class animal
    {
        public virtual void DU()
        {
        }
    }
    class dog : animal
    {
        public override void DU()
        {
           
            Console.WriteLine("This is a dog!!");
           
        }
    }
    class cat : animal
    {
        public override void DU()
        {    
            Console.WriteLine("This is a cat!!");
        }
    }
    class an : animal
    {
        public override void DU()
        {     
            Console.WriteLine("This is animal!! ");
        }
    }
}

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

namespace Animal

{   

  class Program

    {      

   static void Main(string[] args)    

     {             

            dog s = new dog();       

              s.DU();              

       cat j = new cat();          

           j.DU();                   

  an y = new an();             

        y.DU();

            Console.Read();     

    }   

  }

}

11.