索引器

一。声明与使用

      像数组一样访问数据，像属性一样的经构

using System;

namespace Indexer
{
    class Employee
    {
        private string LastName;
        private string FirstName;
        private string CityOfBirth;

        public string this[int index]
        {
            set
            {
                switch(index)
                {
                    case 0: LastName = value;
                        break;
                    case 1: FirstName = value;
                        break;
                    case 2: CityOfBirth = value;
                        break;

                    default:
                        throw new ArgumentOutOfRangeException("index");
                }
            }

            get
            {
                switch(index)
                {
                    case 0: return LastName;
                    case 1: return FirstName;
                    case 2: return CityOfBirth;

                    default:
                        throw new ArgumentOutOfRangeException("index");
                }
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Employee employee = new Employee();
            employee[0] = "Qian";
            employee[1] = "Keefe";
            employee[2] = "LuJiang";

            Console.WriteLine($"{employee[0]} {employee[1]} {employee[2]}");
        }
    }
}

二。索引器重载

using System;

namespace IndexerOverload
{
    class MyClass
    {
        string Temp0;
        string Temp1;
        string Temp2;
        string Temp3;

        int MyInt0 = 0;
        int MyInt1 = 1;

        public string this[int index]
        {
            get
            {
                return (0 == index) ? Temp0 : Temp1;
            }
            set
            {
                if (0 == index) Temp0 = value;
                else Temp1 = value;
            }
        }

        public string this[int index1, int index2]
        {
            get
            {
                if (index1 == 0 && index2 == 0) return Temp0;
                if (index1 == 0 && index2 == 1) return Temp1;
                if (index1 == 1 && index2 == 0) return Temp2;
                if (index1 == 1 && index2 == 1) return Temp3;

                throw new ArgumentOutOfRangeException("index");
            }
            set
            {
                if (index1 == 0 && index2 == 0) Temp0 = value;
                if (index1 == 0 && index2 == 1) Temp1 = value;
                if (index1 == 1 && index2 == 0) Temp2 = value;
                if (index1 == 1 && index2 == 1) Temp3 = value;

                //throw new ArgumentOutOfRangeException("index");
            }
        }


        public int this[float index]
        {
            get
            {
                if (index < 1.0)
                {
                    return MyInt0;
                }
                else
                {
                    return MyInt1;
                }
            }
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MyClass mc = new MyClass();
            mc[0] = "Illustrated";
            mc[1] = "C# 7";
            Console.WriteLine($"{mc[0]} {mc[1]}");

            mc[1, 0] = "Fifth Edition";
            mc[1, 1] = "Daniel Solis & Cal Schrotenboer";
            Console.WriteLine($"{mc[0]} {mc[1]} {mc[1, 0]} {mc[1, 1]}");

            Console.WriteLine($"{mc[0.4f]} {mc[1.3f]}");
        }
    }
}