索引器

      通过对类定义个索引器可以把对象的域当做一个数组元素。例如在Car类中定义一个索引器，用来读写make和model域，定义一个类myCar

myCar[0]访问make,myCar[1]访问model。

/*
  Example10_11.cs illustrates the use of an indexer
*/

using System;


// declare the Car class
public class Car
{

  // declare two fields
  private string make;
  private string model;

  // define a constructor
  public Car(string make, string model)
  {
    this.make = make;
    this.model = model;
  }

  // define the indexer
  public string this[int index]
  {
    get
    {
      switch (index)
      {
        case 0:
          return make;
        case 1:
          return model;
        default:
          throw new IndexOutOfRangeException();
      }
    }
    set
    {
      switch (index)
      {
        case 0:
          this.make = value;
          break;
        case 1:
          this.model = value;
          break;
        default:
          throw new IndexOutOfRangeException();
      }
    }
  }

}


class Example10_11
{

  public static void Main()
  {

    // create a Car object
    Car myCar = new Car("Toyota", "MR2");

    // display myCar[0] and myCar[1]
    Console.WriteLine("myCar[0] = " + myCar[0]);
    Console.WriteLine("myCar[1] = " + myCar[1]);

    // set myCar[0] to "Porsche" and myCar[1] to "Boxster"
    Console.WriteLine("Setting myCar[0] to \"Porsche\" " +
      "and myCar[1] to \"Boxster\"");
    myCar[0] = "Porsche";
    myCar[1] = "Boxster";
    // myCar[2] = "Test";  // causes IndeXOutOfRangeException to be thrown

    // display myCar[0] and myCar[1] again
    Console.WriteLine("myCar[0] = " + myCar[0]);
    Console.WriteLine("myCar[1] = " + myCar[1]);

  }

}