1: interface IPupilRule
   2: {
   3:     void CrossTheRoad(int trafficLightIndex);
   4: }

   1: interface IYoungPioneerRule
   2: {
   3:     void NoSmoke();
   4: }

   1: public class Pupil : IPupilRule
   2: {
   3:     /// <summary>
   4:     /// Cross the road and notice the traffic light.
   5:     /// </summary>
   6:     /// <param name="trafficLightIndex">The index of traffic light.</param>
   7:     public void CrossTheRoad(int trafficLightIndex)
   8:     {
   9:         switch (trafficLightIndex)
  10:         {
  11:             case 0:     // Red, stop.
  12:                 break;
  13:             case 1:     // Yellow, stop.
  14:                 break;
  15:             case 2:     // Green, go.
  16:                 break;
  17:             default:    // Unknown situation, thinking.
  18:                 break;
  19:         }
  20:     }
  21: }

1: public class YoungPioneer : Pupil, IYoungPioneerRule
   2: {
   3:     /// <summary>
   4:     /// Young pioneer should help other people.
   5:     /// </summary>
   6:     public void NoSmoke()
   7:     {
   8:         throw new NotImplementedException("I can't smoke because I'm a young pioneer.");
   9:     }
  10: }

   1: interface IXiangYangSchoolRule : IPupilRule, IYoungPioneerRule
   2: {
   3:     void SingSchoolSong();
   4: }

  1: public class XiangYangPupil : IXiangYangSchoolRule
   2: {
   3:     public void SingSchoolSong()
   4:     {
   5:         Console.WriteLine("I love Xiang Yang School!");
   6:     }
   7:  
   8:     public void CrossTheRoad(int trafficLightIndex)
   9:     {
  10:         throw new NotImplementedException();
  11:     }
  12:  
  13:     public void NoSmoke()
  14:     {
  15:         throw new NotImplementedException();
  16:     }
  17: }

    class Data : IComparable //实现IComparable接口;
    {
        public int data;
        public int CompareTo(object obj)
        {
            Data mc = (Data)obj;
            if (this.data > mc.data)
            {
                return 1;
            }
            else if (this.data < mc.data)
            {
                return -1;
            }
            return 0;
        }
    }
    class Program 
    {
        static void Main(string[] args)
        {
            var myInt = new []{ 23, 5, 7, 9, 3 };
            Data []data = new Data[5];
            for(int i=0;i<5;i++)
            {
                data[i] = new Data();
                data[i].data = myInt[i];
            }
            Array.Sort(data);
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine(data[i].data);
            }
        }
    }