一道.NET题

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

namespace  TestApplication
{

     class  Program
    {
         static  List < Student >  stus  =   new  List < Student > ();  //  存储学生的索引及其平均分
         ///   <summary>
         ///  程序入口
         ///   </summary>
         static   void  Main( string [] args)
        {
            Console.Write( " 输入同学人数（最多15人）： " );
             string  num  =  Console.ReadLine();
             int  count;
             if  ( int .TryParse(num,  out  count))
            {
                 if  (count  <   1   ||  count  >   15 )
                {
                    Console.WriteLine( " 请输入1~15之间的数字，程序退出！ " );
                    Console.ReadLine();
                     return ;
                }
                 string [] scours  =   new   string [count];   //  存储每位同学的成绩字符串，如:80, 70, 60
                 //  循环输入成绩
                 for  ( int  i  =   0 ; i  <  count; i ++ )
                {
                    Console.Write( " 输入第 "   +  (i  +   1 )  +   " 位同学小考成绩： " );
                    scours[i]  =  Console.ReadLine();
                }
                Console.WriteLine( " =============================================== " );
                 //  循环输出平均成绩
                 for  ( int  i  =   0 ; i  <  count; i ++ )
                {
                    Console.WriteLine( " 第 "   +  (i  +   1 )  +   " 位同学平均： "   +  CalcAvg(scours[i], i  +   1 ));
                }
                Console.WriteLine( " =============================================== " );
                 //  输出分数排名
                StudentComparer sc  =   new  StudentComparer();
                stus.Sort(sc);
                 for  ( int  i  =   0 ; i  <  stus.Count; i ++ )
                {
                    Console.WriteLine( " 第 "   +  (i  +   1 )  +   " 高分为第 "   +  stus[i].Index  +   " 位同学： "   +  stus[i].Avg);
                }
            }
             else
            {
                Console.WriteLine( " 格式输入错误，请输入数字，程序退出！ " );
            }
            Console.Read();
        }

         ///   <summary> 计算成绩字符串的平均值
         ///  
         ///   </summary>
         ///   <param name="p"> 成绩字符串，如：80,70,50 </param>
         ///   <param name="index"> 该同学的索引 </param>
         ///   <returns></returns>
         private   static   string  CalcAvg( string  p,  int  index)
        {
             string [] ss  =  p.Split( new   char [] {  ' , '  });

             if  (ss.Length  ==   0 )
            {
                 return   " 成绩输入错误，请按“80,70,50”的格式输入！ " ;
            }
             else
            {
                 int  i  =   0 ;
                 float  total  =  0f;
                 foreach  ( string  str  in  ss)
                {
                     float  f;
                     if  ( float .TryParse(str,  out  f))
                    {
                        i ++ ;
                        total  +=  f;
                    }
                     else
                    {
                         return   " 成绩输入错误，请按“80,70,50”的格式输入！ " ;
                    }
                }
                 float  avg  =  total  /  i;  //  平均分
                stus.Add( new  Student(index, avg));   //  把当前同学的平均分及其索引加到List中        
                 return  avg.ToString();
            }
        }
    }

     ///   <summary>
     ///  学生实体类
     ///   </summary>
     public   class  Student
    {
         private   int  _index;
         ///   <summary>
         ///  索引
         ///   </summary>
         public   int  Index
        {
             get  {  return  _index; }
             set  { _index  =  value; }
        }
         private   float  _avg;
         ///   <summary>
         ///   平均分
         ///   </summary>
         public   float  Avg
        {
             get  {  return  _avg; }
             set  { _avg  =  value; }
        }

         public  Student( int  index,  float  avg)
        {
             this ._index  =  index;
             this ._avg  =  avg;
        }
    }

     ///   <summary>
     ///  学生实体类的比较，按学生的平均分从高到低排列
     ///   </summary>
     public   class  StudentComparer : IComparer < Student >
    {
         public   int  Compare(Student x, Student y)
        {
             if  (x  ==   null )
            {
                 if  (y  ==   null )
                {
                     //  如果二者都为空，那么他们则是相等的. 
                     return   0 ;
                }
                 else
                {
                     //  如果X为空而Y不为空，则Y大
                     return   - 1 ;
                }
            }
             else
            {
                 if  (y  ==   null )
                 //  如果X不为空而Y为空，则X大
                {
                     return   1 ;
                }
                 else
                {
                     //  二者都不为空，则比较其中的avg属性
                     float  x_avg  =  x.Avg;
                     float  y_avg  =  y.Avg;
                     return  y_avg.CompareTo(x_avg);   // 此为从大到小，若是 x_avg.CompareTo(y_avg)则是从小到大
                }
            }
        }
    }
}