Short note on Collection .

 Collection 

- For many applications, you want to create and manage groups of related objects. There are two ways to group objects: by creating arrays of objects, and by creating collections of objects Arrays are most useful for creating and working with a fixed number of strongly typed objects. 

- Collections provide a more flexible way to work with groups of objects. Unlike arrays, the group of objects you work with can grow and shrink dynamically as the needs of the application change. For some collections, you can assign a key to any object that you put into the collection so that you can quickly retrieve the object by using the key.

- A collection is a class, so you must declare an instance of the class before you can add an element to that collection.

Example 

using System;

using System.Collections;

namespace CollectionApplication {

class Program {

static void Main(string[] args) {

ArrayList al = new ArrayList(); Console.WriteLine("Adding some numbers:");

al.Add(45);

al.Add(78);

al.Add(33); 

al.Add(56);

al.Add(12);

al.Add(23);

al.Add(9);

Console.WriteLine("Capacity: (0)", al.Capacity);

Console.WriteLine("Count: (0)", al.Count); Console.Write("Content: ");

foreach (int i in al){

Console.Write(i + " ");

Console.WriteLine();

Console.Write("Sorted Content: ");

al.Sort();

foreach (int i in al) 

{

Console.Write(i + " ");

}

Console.WriteLine(); 

Console.ReadKey();

}

}

}