自己写的一个字符索引器,有关于效率和代价问题请教各位

今天早上醒来精神不错，就写了一个字符索引器，希望各位指出不足之处，无论是编程习惯还是缺陷！

  1using System;
  2
  3namespace Company
  4{
  5    /**//// <summary>
  6    /// Class1 的摘要说明。
  7    /// </summary>
  8    public class Company
  9    {
 10        public string   Name; 
 11        private Employee[] emp;
 12        System.Collections.ArrayList indexList=new System.Collections.ArrayList();//存储字符索引的数组
 13        private static int   i=0;
 14
 15        public Company(string n)
 16        {
 17            this.Name = n;
 18            emp=new Employee[100];
 19        } 
 20        public Employee this [int index]
 21        {
 22            get
 23            {
 24                if(indexList.Count<index)//整型索引超出边界
 25                {
 26                    //throw Exception;
 27                    return null;
 28                }
 29                else
 30                    return emp[index];
 31            }
 32            set
 33            {
 34                if (value != null)
 35                {
 36                    emp [index] = value;
 37                }
 38            }
 39        }//indexer
 40        public Employee this [string index]
 41        {
 42            get
 43            {
 44                return emp[GetIndex(index)];
 45            }
 46            set
 47            {
 48                if (value != null)//Company[]的值不为空
 49                {
 50                    if(indexList.Count==0)
 51                    {
 52                        indexList.Add(index);
 53                        i++;
 54                        emp[GetIndex(index)] = value;
 55                    }
 56                    else
 57                    {
 58                        for(int j=0;j< indexList.Count;j++)
 59                        {                                    
 60                            if(index!=(string)indexList[j])//判断字符索引是否重复
 61                            {
 62                                indexList.Add(index);//相索引列表中添加索引值
 63                                i++;
 64                                emp [GetIndex(index)] = value;
 65                            }
 66                            else
 67                            {
 68                                emp [GetIndex(index)] = value;//如果重复则覆盖原来的实例
 69                            }
 70                        }
 71                    }
 72                }
 73            }
 74        }//indexer
 75        private int GetIndex(string index)//根据字符索引返回整型索引
 76        {
 77            int i=0;
 78            for(int j=0;j<indexList.Count;j++)
 79            {
 80                if(index==(string)indexList[j])
 81                {
 82                    return i;
 83                }
 84                i++;
 85            }
 86            return -1;
 87        }
 88        
 89    }
 90    public class Employee
 91    {
 92        private string name;
 93        public Employee(string n)
 94        {
 95            this.name=n;
 96        }
 97        public string Name
 98        {
 99            get
100            {
101                return this.name;
102            }
103        }
104    }
105    public class test
106    {
107        static void Main()
108        {
109            Company c=new Company("company");
110            c["employe"]=new Employee("emp1");
111            c["employe"]=new Employee("emp2");
112            Console.WriteLine(c[0].Name);
113        }
114    }
115
116}
117

这里有个问题,在实际应用中，如果出现了
c["employe"]=new Employee("emp1");
c["employe"]=new Employee("emp2");
对于c["employe"]应该是覆盖，还是直接indexList.Add(index);（第48行）
到底应不应该判断索引标签是否重复的那段？
如果不判断，indexList（ArrayList类型）就会庞大，出现c[0]=c[1]
如果判断，在算法的复杂度就会增加一个级别.
我应该怎么办啊？？？？