C#學習筆記（八）——集合、比較和轉換

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一、集合

** System.Collections名稱空間中的幾個介面提供了基本的集合功能

Ps：這裡看成一個動態鏈表，但是已經完美的封裝好了。

一、使用集合

1、程式碼範例

（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)        {        }    }}

（4）Program.cs

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、運行結果

3、注意點：

（1）ArrayList建立時不需要指定初始長度值。但是Array是需要的。

（2）對於ArrayList是不強調類型的一個集合，所以再採用所屬對象的方法之類的時候，必須進行強制類型轉換，而對於Array來說，他是強調物件類型的集合，所以可以直接調用其方法，但是對於其衍生類別來說，還是需要進行強制類型轉換。

（3）還有些刪除（at）和擴充方法（AddRange）之類的擴充方法

（4）ArrayList需要加上using System.Collections;名字空間的引用，切記切記。

C#學習筆記（八）——集合、比較和轉換