Collection<T>

1. 可以Index存取元素.
2. 元素可以為null.
3. 元素可以重複.

Example1

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

public class Demo
{
public static void Main()
{
Collection<string> dinosaurs = new Collection<string>();

dinosaurs.Add("Psitticosaurus");
dinosaurs.Add("Caudipteryx");
dinosaurs.Add("Compsognathus");
dinosaurs.Add("Muttaburrasaurus");

Console.WriteLine("{0} dinosaurs:", dinosaurs.Count);
Display(dinosaurs);

Console.WriteLine("\nIndexOf(\"Muttaburrasaurus\"): {0}", 
dinosaurs.IndexOf("Muttaburrasaurus"));

Console.WriteLine("\nContains(\"Caudipteryx\"): {0}", 
dinosaurs.Contains("Caudipteryx"));

Console.WriteLine("\nInsert(2, \"Nanotyrannus\")");
dinosaurs.Insert(2, "Nanotyrannus");
Display(dinosaurs);

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

Console.WriteLine("\ndinosaurs[2] = \"Microraptor\"");
dinosaurs[2] = "Microraptor";
Display(dinosaurs);

Console.WriteLine("\nRemove(\"Microraptor\")");
dinosaurs.Remove("Microraptor");
Display(dinosaurs);

Console.WriteLine("\nRemoveAt(0)");
dinosaurs.RemoveAt(0);
Display(dinosaurs);

Console.WriteLine("\ndinosaurs.Clear()");
dinosaurs.Clear();
Console.WriteLine("Count: {0}", dinosaurs.Count);
}

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

/* This code example produces the following output:

4 dinosaurs:

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

IndexOf("Muttaburrasaurus"): 3

Contains("Caudipteryx"): True

Insert(2, "Nanotyrannus")

Psitticosaurus
Caudipteryx
Nanotyrannus
Compsognathus
Muttaburrasaurus

dinosaurs[2]: Nanotyrannus

dinosaurs[2] = "Microraptor"

Psitticosaurus
Caudipteryx
Microraptor
Compsognathus
Muttaburrasaurus

Remove("Microraptor")

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

RemoveAt(0)

Caudipteryx
Compsognathus
Muttaburrasaurus

dinosaurs.Clear()
Count: 0
*/

Example2

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

public class Dinosaurs : Collection<string>
{
public event EventHandler<DinosaursChangedEventArgs> Changed;

protected override void InsertItem(int index, string newItem)
{
base.InsertItem(index, newItem);

EventHandler<DinosaursChangedEventArgs> temp = Changed;
if (temp != null)
{
temp(this, new DinosaursChangedEventArgs(
ChangeType.Added, newItem, null));
}
}

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));
}
}

protected override void RemoveItem(int index)
{
string removedItem = Items[index];
base.RemoveItem(index);

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));
}
}
}

// Event argument for the Changed event.
//
public class DinosaursChangedEventArgs : EventArgs
{
public readonly string ChangedItem;
public readonly ChangeType ChangeType;
public readonly string ReplacedWith;

public DinosaursChangedEventArgs(ChangeType change, string item, 
string replacement)
{
ChangeType = change;
ChangedItem = item;
ReplacedWith = replacement;
}
}

public enum ChangeType
{
Added, 
Removed, 
Replaced, 
Cleared
};

public class Demo
{
public static void Main()
{
Dinosaurs dinosaurs = new Dinosaurs();

dinosaurs.Changed += ChangedHandler; 

dinosaurs.Add("Psitticosaurus");
dinosaurs.Add("Caudipteryx");
dinosaurs.Add("Compsognathus");
dinosaurs.Add("Muttaburrasaurus");

Display(dinosaurs);

Console.WriteLine("\nIndexOf(\"Muttaburrasaurus\"): {0}", 
dinosaurs.IndexOf("Muttaburrasaurus"));

Console.WriteLine("\nContains(\"Caudipteryx\"): {0}", 
dinosaurs.Contains("Caudipteryx"));

Console.WriteLine("\nInsert(2, \"Nanotyrannus\")");
dinosaurs.Insert(2, "Nanotyrannus");

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

Console.WriteLine("\ndinosaurs[2] = \"Microraptor\"");
dinosaurs[2] = "Microraptor";

Console.WriteLine("\nRemove(\"Microraptor\")");
dinosaurs.Remove("Microraptor");

Console.WriteLine("\nRemoveAt(0)");
dinosaurs.RemoveAt(0);

Display(dinosaurs);
}

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

private static void ChangedHandler(object source, 
DinosaursChangedEventArgs e)
{

if (e.ChangeType==ChangeType.Replaced)
{
Console.WriteLine("{0} was replaced with {1}", e.ChangedItem, 
e.ReplacedWith);
}
else if(e.ChangeType==ChangeType.Cleared)
{
Console.WriteLine("The dinosaur list was cleared.");
}
else
{
Console.WriteLine("{0} was {1}.", e.ChangedItem, e.ChangeType);
}
}
}

/* This code example produces the following output:

Psitticosaurus was Added.
Caudipteryx was Added.
Compsognathus was Added.
Muttaburrasaurus was Added.

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

IndexOf("Muttaburrasaurus"): 3

Contains("Caudipteryx"): True

Insert(2, "Nanotyrannus")
Nanotyrannus was Added.

dinosaurs[2]: Nanotyrannus

dinosaurs[2] = "Microraptor"
Nanotyrannus was replaced with Microraptor

Remove("Microraptor")
Microraptor was Removed.

RemoveAt(0)
Psitticosaurus was Removed.

Caudipteryx
Compsognathus
Muttaburrasaurus
*/