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C#学习笔记（八）——集合、比较和转换
一、集合
** System.Collections名称空间中的几个接口提供了基本的集合功能
Ps：这里看成一个动态的链表，但是已经完美的封装好了。
一、使用集合
1、代码示例
（1）Animal.cs
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace Exercise{ public abstract class Animal { protected string name; public string Name { get { return name; } set { name = value; } } public Animal() { name = "The animal with no name"; } public Animal(string newName) { name = newName; } public void Feed() { Console.WriteLine("{0} has been fed", name); } }}
（2）Cow.cs
namespace Exercise{ public class Cow:Animal { public void Milk() { Console.WriteLine("{0} has been milked.", name); } public Cow(string newName):base(newName) { } }}
（3）Chicken.cs
namespace Exercise{ public class Chicken:Animal { public void LayEgg() { Console.WriteLine("{0} has laid an egg.", name); } public Chicken(string newName):base(newName) { } }}
namespace Exercise{ class Program { static void Main(string[] args) { Console.WriteLine("Create an Array type collection of Animal " + "objects and use it:"); Animal[] animalAraay = new Animal[2]; Cow myCowl = new Cow("Deirdre"); animalAraay[0] = myCowl; animalAraay[1] = new Chicken("Ken"); foreach(Animal myAnimal in animalAraay) { Console.WriteLine("New {0} object added to Array collection, " + "Name = {1}", myAnimal.ToString(), myAnimal.Name); } Console.WriteLine("Array collection contains {0} objects.", animalAraay.Length); animalAraay[0].Feed(); ((Chicken)animalAraay[1]).LayEgg(); Console.WriteLine(); Console.ReadKey(); Console.WriteLine("Create an ArrayList type collection of Animal " + "object and use it "); ArrayList animalArrayList = new ArrayList(); Cow mycow2 = new Cow("Heylay"); animalArrayList.Add(mycow2); animalArrayList.Add(new Chicken("Roy")); foreach(Animal myAnimal in animalArrayList) { Console.WriteLine("New {0} object added to ArrayList collection," + "Name = {1}", myAnimal.ToString(), myAnimal.Name); } Console.WriteLine("ArrayList collection contains {0} objects.", animalArrayList.Count); ((Animal)animalArrayList[0]).Feed(); ((Chicken)animalArrayList[1]).LayEgg(); Console.WriteLine(); Console.WriteLine("Additional manipulation of ArrayList:"); animalArrayList.RemoveAt(0); ((Animal)animalArrayList[0]).Feed(); animalArrayList.AddRange(animalAraay); ((Chicken)animalArrayList[2]).LayEgg(); Console.WriteLine("The animal called {0} is at index {1}.", myCowl.Name, animalArrayList.IndexOf(myCowl)); myCowl.Name = "Janice"; Console.WriteLine("The animal is now called {0}.", ((Animal)animalArrayList[1]).Name); Console.ReadKey(); } }}
2、运行结果
3、注意点：
（1）ArrayList创建时不需要指定初始长度值。但是Array是需要的。
（2）对于ArrayList是不强调类型的一个集合，所以再采用所属对象的方法之类的时候，必须进行强制类型转换，而对于Array来说，他是强调对象类型的集合，所以可以直接调用其方法，但是对于其派生类来说，还是需要进行强制类型转换。
（3）还有些删除（at）和扩展方法（AddRange）之类的扩展方法
（4）ArrayList需要加上using System.Collections;名字空间的引用，切记切记。
C#学习笔记（八）——集合、比较和转换
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