集合泛型的使用

该例子来自于微软官方,虽然讲的很好,但是个人的理解还是非常不到位的。特别是关于委托管理的细节问题，梳理得不是特别清楚。将其摘要于下。也希望牛人将其结构予以较完整的疏离，特别是其中事件触发地方。

该例子是对通过基于集合的泛型类来构建一个自定义的类，并且基于四个方法，重写了其增删改查的操作。

该例子是通过一个改变的改变的通知事件，在每一个方法的最后被触发。其中，DinosaursChangedEventArgs被作为事件信息。

Program.cs

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

namespace Collection_Generic2
{
    class Program
    {
        static void Main(string[] args)
        {
            //初始化类
            dinosaurs dino = new dinosaurs();

            dino.Changed += ChangeHandler;
//这个地方理解的不是很好
            dino.Add("Psiticosaurus");
            dino.Add("Caudipteryx");
            dino.Add("Compsognathus");
            dino.Add("Muttaburrasaurus");

            Display(dino);

            Console.WriteLine("\n IndexOf(\"Muttaburrasaurus\"):{0}", dino.IndexOf("Muttaburrasaurus"));

            Console.WriteLine("\n Contains(\"Caudipteryx\"):{0}",
                dino.Contains("Caudipteryx"));

            Console.WriteLine("\n Insert(2,\"Nanotyrannus\")");
                dino.Insert(2,"Nanotyrannus"); 

            Console.WriteLine("\n dino[2]:{0}",dino[2]);

            Console.WriteLine("\n dino[2]=\"Microraptor\"",
                dino[2]="Microraptor");

            Console.WriteLine("\n Remove (\"Microraptor\")");
            dino.Remove("Microraptor");

            Console.WriteLine("\n RemoveAt(0)");
            dino.RemoveAt(0);

            Display(dino);

            Console.ReadLine();
        }

        private static void ChangeHandler(object source, dinosaursChangedEventArgs e)
        {
            if (e.ChangeType == ChangeType.Replaced)
            {
                Console.WriteLine("{0} was replaced with {1}", e.ChangedItem, e.ReplaceWith);
            }
            else if (e.ChangeType == ChangeType.Cleared)
            {
                Console.WriteLine("The dinosaur list was cleared");
            }
            else
            {
                Console.WriteLine("{0} was {1}", e.ChangedItem, e.ChangeType);
            }
        }

        private static void Display(Collection<string> cs)
        {
            Console.WriteLine();
            foreach (string item in cs)
            {
                Console.WriteLine(item);
            }
        }
    }
}

dinosaurs.cs

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

namespace Collection_Generic2
{
    //继承泛型集合
    class dinosaurs : Collection<string>
    {
        //该处类似于侦查其是否发送改变，一旦发生改变，则触发方法
        public event EventHandler<dinosaursChangedEventArgs> Changed;

        /// <summary>
        /// 重写InsertItem方法
        /// </summary>
        /// <param name="index"></param>
        /// <param name="item"></param>
        protected override void InsertItem(int index, string newItem)
        {
            base.InsertItem(index, newItem);

            EventHandler<dinosaursChangedEventArgs> temp = Changed;

            if (temp != null)//增强稳健型
            {
                //如果发生改变，那么就添加一个新的项目进入指定位置
                //this在这里是什么作用呢?没有想得特别明白
                temp(this, new dinosaursChangedEventArgs(ChangeType.Added, newItem, null));
            }
        }

        /// <summary>
        /// 这个更换的功能的重写
        /// </summary>
        /// <param name="index"></param>
        /// <param name="NewItem"></param>
        protected override void SetItem(int index, string NewItem)
        {
            string replaced = Items[index];
            base.SetItem(index, NewItem);

            EventHandler<dinosaursChangedEventArgs> temp = Changed;

            if (temp != null)
            {
                temp(this, new dinosaursChangedEventArgs(ChangeType.Replaced, replaced, NewItem));
            }
        }

        /// <summary>
        /// 重写移除操作
        /// </summary>
        /// <param name="index"></param>
        protected override void RemoveItem(int index)
        {
            //Items获取其列表的内容
            string removedItem = Items[index];
            base.RemoveItem(index);
            //代理改变这一事件,将其进行赋值
            EventHandler<dinosaursChangedEventArgs> temp = Changed;
            if (temp != null)
            {
                temp(this, new dinosaursChangedEventArgs(ChangeType.Removed, removedItem, null));
            }
        }

        protected override void ClearItems()
        {
            base.ClearItems();

            EventHandler<dinosaursChangedEventArgs> temp = Changed;

            if (temp!=null)
            {
                temp(this,new dinosaursChangedEventArgs(ChangeType.Cleared,null,null));
            }
        }

    }

    /// <summary>
    /// 改变的事件的参数
    /// </summary>
    public class dinosaursChangedEventArgs : EventArgs
    {
        public readonly string ChangedItem;
        public readonly ChangeType ChangeType;
        public readonly string ReplaceWith;

        /// <summary>
        /// 和类名相同，这样它应该算作重载
        /// 其内容是通过重载，对类的三个属性进行赋值
        /// </summary>
        /// <param name="change"></param>
        /// <param name="item"></param>
        /// <param name="replacement"></param>
        public dinosaursChangedEventArgs(ChangeType change, string item, string replacement)
        {
            ChangeType = change;
            ChangedItem = item;
            ReplaceWith = replacement;
        }

    }

    /// <summary>
    /// 将类型的四种操作实现枚举，枚举定义后面需要增加分号
    /// 因为是一个定义，而非方法或类
    /// </summary>
    public enum ChangeType
    {
        Added,
        Removed,
        Replaced,
        Cleared
    };
}