C#类索引器的使用

Posted 2020-07-09

索引器提供了一种可以让类被当作数组进行访问的方式。在C#中，类索引器是通过this的属性实现的。
index.ToString("D2")将index转换成一个具有两个字符宽度的字符串

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

namespace ClassIndexer
{
    /// <summary>
    /// define a class called AClass,which has only one private variable
    /// </summary>
   class AClass {
       private string _name;
       public string Name {
           get { return this._name; }
           set { this._name = value; }
       }
       public AClass(string name) {
           this._name = name;
       }
    }
    /// <summary>
    /// AClassContainer class
    /// </summary>
   class AClassContainer {
       private AClass[] _AClassList;
       public AClassContainer() {
           this._AClassList = new AClass[10];
       }
       public AClassContainer(int cap) {
           this._AClassList = new AClass[cap];
       }
       /// <summary>
       /// class indexer by using int 
       /// </summary>
       /// <param name="index"></param>
       /// <returns></returns>
       public AClass this[int index] {
           get {
               if ((index < 0) || (index > this._AClassList.Length)) return null;
               else return this._AClassList[index];
           }
           set {
               if ((index < 0) || (index > this._AClassList.Length)) return;
               else this._AClassList[index] = value;
           }
       }
       /// <summary>
       /// class indexer by using string
       /// </summary>
       /// <param name="name"></param>
       /// <returns></returns>
       public AClass this[string name] {
           get {
               foreach (AClass cls in this._AClassList) {
                   if (cls.Name == name) return cls;
               }
               return null;
           }
       }
   }
    class Program
    {
        static void Main(string[] args)
        {
            int count = 10;
            AClassContainer classContainer = new AClassContainer(count);
            for (int index = 0; index < count; index++) {
                string name = index.ToString("D2");
                classContainer[index] = new AClass(name);
            }
            for (int index = 0; index < count; index++)
            {
                AClass cls = classContainer[index];
                System.Console.WriteLine("classContainer[{0}].Name=\"{1}\"",index,cls.Name);
            }
            System.Console.WriteLine();
            for (int index = count - 1; index >= 0; index--) {
                string name = index.ToString("D2");
                AClass cls = classContainer[name];
                System.Console.WriteLine("classContainer[{0}].Name=\"{1}\"",name,cls.Name);
            }
            System.Console.ReadLine();
        }
    }
}

结果：
classContainer[0].Name="00"
classContainer[1].Name="01"
classContainer[2].Name="02"
classContainer[3].Name="03"
classContainer[4].Name="04"
classContainer[5].Name="05"
classContainer[6].Name="06"
classContainer[7].Name="07"
classContainer[8].Name="08"
classContainer[9].Name="09"

classContainer[09].Name="09"
classContainer[08].Name="08"
classContainer[07].Name="07"
classContainer[06].Name="06"
classContainer[05].Name="05"
classContainer[04].Name="04"
classContainer[03].Name="03"
classContainer[02].Name="02"
classContainer[01].Name="01"
classContainer[00].Name="00"