Collections in c#

Collections

Collection is special type of classes in that we can add data and retrieve from it. It support some properties which is useful while doing programming. These classes provide support for stack, queue, hash set, array list. Collection classes present in System.Collections namespace.

ArrayList:

Arraylist size is not fixed. It grows dynamically. You can use add and remove method for adding and removing item from arraylist. In ArrayList we can add any type of data. It’s not fixed.

Example:

ArrayList arr = new ArrayList();

arr.Add("abd");

arr.Add(12);

Stack Collection:

Stack is a collection of type LIFO means last in first out collection. We can retrieve items from stack like first item can remove at last.

There is Push method of stack to be used for adding item in stack.

Example:

using System;

using System.Collections.Generic;

using System.Collections;

namespace ConsoleApplication5

{

    class Program

    {

        static void Main(string[] args)

        {

            Stack<int> stk = new Stack<int>();

            stk.Push(1);

            stk.Push(2);

            stk.Push(3);

            foreach (int i in stk)

            {

                Console.WriteLine(i);

            }

            Console.ReadLine();

        }

    }

}

Output:

3

2

1

Also we can use pop method to remove and also return next element. Like below

int i= stk.Pop();

It removes and return last element in stack.

Queue Collection:

Queue is a FIFO collection means First-in-First-out collection. In which order they are inserted in collection only that order element get retrieved.

Example:

using System;

using System.Collections.Generic;

using System.Collections;

namespace ConsoleApplication5

{

    class Program

    {

        static void Main(string[] args)

        {

            Queue<int> que = new Queue<int>();

            que.Enqueue(1);

            que.Enqueue(2);

            que.Enqueue(3);

            foreach (int i in que)

            {

                Console.WriteLine(i);

            }

            Console.ReadLine();

        }

    }

}

Output:

1

2

3

In Queue we use Enqueue method to add element in collection.