Boxing and unboxing in C#.net

                 C# Type System contains three Types , they are Value Types , Reference Types and Pointer Types. C# allows us to convert a Value Type to a Reference Type, and back again to Value Types . The operation of Converting a Value Type to a Reference Type is called Boxing and the reverse operation is called Unboxing.

Boxing

  1:           int Val = 1;

  2:           Object Obj = Val; //Boxing

                  The first line we created a Value Type Val and assigned a value to Val. The second line , we created an instance of Object Obj and assign the value of Val to Obj. From the above operation (Object Obj = i ) we saw converting a value of a Value Type into a value of a corresponding Reference Type . These types of operation is called Boxing.

UnBoxing

  1:           int Val = 1;

  2:           Object Obj = Val; //Boxing

  3:           int i = (int)Obj; //Unboxing

               The first two line shows how to Box a Value Type . The next line (int i = (int) Obj) shows extracts the Value Type from the Object . That is converting a value of a Reference Type into a value of a Value Type. This operation is called UnBoxing.

Boxing and UnBoxing are computationally expensive processes. When a value type is boxed, an entirely new object must be allocated and constructed , also the cast required for UnBoxing is also expensive computationally.

using System;

using System.Windows.Forms;

namespace WindowsApplication1

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            int Val = 1;

            Object Obj = Val;            //Boxing

            int i = (int)Obj;            //Unboxing

            MessageBox.Show("The value is   : " + i);

        }

    }

}