求以个程序的解析！！！！！
namespace Test11
{
    class Ball
    {
        string[] winners;                              
        int [] prize;                                  
        int winner;                                    
        public Ball(int length)                                               
        {
            winners = new string[length];               
            prize = new int [length];                                             
         }
        public string Winner                            
        {
            set
            {
                winners[winner] = value;                
            }
        }
        public int this[int index]                      
        {
            get
            {
                return prize[index];                    
            }
            set
            {
                prize[in