利用索引器取值 赋值
案例1

c#
// 创建Test.cs  类
    class Test
    {
        public string this[int index]
        {
            get
            {
                Console.WriteLine([index]);
                return 100；            
            }
            set
            {
               Console.WriteLine([index]);
               Console.WriteLine(value);
            }
        }
    }

c#
//使用 Program.cs
            Test t = new Test();  
            
            t[9] = 200;
            Console.WriteLine(t[9]);

案例2

c#
// 创建Test.cs  类
    class Test
    {

        private string[] name = new string[10];

        public string this[int index]
        {
            get
            {
                return name[index];
            }
            set
            {
                name[index] = value;
            }
        }
    }

c#
//使用 Program.cs
            Test t = new Test();
            t[0] = "张三";
            t[1] = "李四";   //赋值

            Console.WriteLine(t[0]);
            Console.WriteLine(t[1]);  //取值

案例3

c#
// 创建Week.cs  类
    class Week
    {
        private string[] days = { "Mon", "Tues", "Wed", "Thu", "Fri", "Sat", "Sun" };

       // public int GetDay(string day)  //传递英文返回数值    
        private int GetDay(string day)  //使用方法2索引时，需将public改为private
        {
            int i = 0;  //开始传递
            foreach(string temp in days)
            {
                if (temp == day) return i+1;  //找到索引
                i++;
            }
            return -1;
        }

        public int this[string day]
        {
            get
            {
                return GetDay(day);  //调用上面的方法
            }
        }
    }

c#
//使用 Program.cs
            //方法1
            Week w = new Week();
            Console.WriteLine(w.GetDay("Thu"));
            //方法2
            Console.WriteLine(w["Sat"]);