Boxing and Unboxing in .NET
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by Sandeep Acharya
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What is Boxing and UnBoxing?

Boxing and Unboxing are two important portions of .NET technology. Many of the developers are not really aware of it, but it is really needed if somebody is interested in enhancing the performance of the application developed.

In a very brief way, one can say that Boxing is nothing but converting a value type object to a reference type object. Unboxing is completely explicit. The idea will be clearer after discussing the example given below. This example shows how an integer type is converted to a reference type using the boxing and then unboxed from the object type to the integer type.

Listing 4

class Test
{
  static void Main()
  {
    int i = 1; // i is an integer. It is a value type variable.
    object o = i;
      // boxing is happening. The integer type is parsed to //object type
    int j = (int)o;
      // unboxing is happening. The object type is unboxed to //the value type
  }
}

Explanation

In the above example, it is shown how an int value can be converted to an object and back again to an int. This example shows both boxing and unboxing. When a variable of a value type needs to be converted to a reference type, an object box is allocated to hold the value and the value is copied into the box.

Unboxing is just the opposite. When an object box is cast back to its original value type, the value is copied out of the box and into the appropriate storage location.


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Title: what is boxing and unboxing?   
Name: sim
Date: 7/26/2011 12:48:00 PM
Comment:
ya i understud now!!.....
Title: boxing & unboxing   
Name: dharmendra kunar
Date: 4/7/2011 8:58:09 PM
Comment:
i thing here the complete disscus about boxing and unboxing
Title: Web Developer   
Name: Dali
Date: 2/20/2011 3:46:16 PM
Comment:
Thank you much. Keep up your good work.
Title: boxing and un boxing   
Name: Eknath Dohale
Date: 10/7/2010 8:48:07 AM
Comment:
Nice article... Keep it up...!
Title: boxing and un boxing   
Name: Vikas Kumar
Date: 9/19/2010 4:39:42 AM
Comment:
Good Explanation
Title: boxing and un boxing   
Name: shankar
Date: 9/14/2010 2:02:03 AM
Comment:
gr8 work
Title: boxing &unboxing   
Name: lakshmanaro
Date: 7/28/2010 3:28:54 AM
Comment:
what is boxing why are the boxing
Title: need more sample   
Name: walkincg
Date: 7/24/2010 9:26:54 AM
Comment:
we have the value like below
int i = 2;
string str = i.ToString() // is there boxing is performing
int j = 1; //is there unboxing is performing
Title: What is Boxing and UnBoxing?   
Name: vinay h
Date: 5/27/2010 5:34:14 AM
Comment:
Good description..very usefull and easy to understand.
Title: What is Boxing and UnBoxing?   
Name: Sridhar.R
Date: 5/11/2010 2:50:47 AM
Comment:
Hi,

Nice One. and very useful for as u said for being a developer.
Title: Boxing   
Name: Rohan
Date: 2/16/2010 7:22:44 AM
Comment:
nice example..each and every can easily understud..
Title: need more   
Name: nadhiya.s
Date: 8/14/2009 12:04:56 PM
Comment:
nice example.. but i need more example program ya...
thanks
Title: Thanks Shakuntala   
Name: Sandeep Acharya
Date: 8/14/2008 9:42:17 PM
Comment:
Shakuntala,

Thanks for your posting....
But this one seems to be an invalid casting...If it could be a valid conversion then yes it would be an unboxing.
Title: Need clarification on Ex.of Boxing and Unboxing   
Name: Shakuntala
Date: 8/14/2008 3:28:28 AM
Comment:
String is a reference type so
if we declare
string name = "Shalini";
and
int i = Int.Parse(name);(here we are converting refernce type to int type so it is unboxing)
is this correct one??
Title: Boxing and UnBoxing   
Name: Giribabu
Date: 7/11/2008 1:16:55 AM
Comment:
Everyone is using same example, can you tell/ give me real time example's so that anyone can explain to an interviewer who is asking this question. i hope he will not satisfy by simple explaining this concept as it is. I will give you a sample where we use boxing in realtime project, you just explain me about that.

example
---------
Suppose MyTestProject Entity has productID
MyTestProject obj = new MyTestProject();
Session["ProductID"] = obj.productID;

can you explain it?
Title: Boxing & UNBoxing   
Name: prasad
Date: 5/21/2008 5:36:37 AM
Comment:
kinly give me more examples about it and what is the advantages of using boxing&Unboxing.How should explain in the interview.

Note:please write the definition
Title: Boxing & UNBoxing   
Name: venkat
Date: 4/9/2008 4:01:28 AM
Comment:
give me more examples & what is the benifit
send me mail:rams.marni@gmail.com
Title: Boxing & UNBoxing   
Name: Shashi
Date: 3/23/2008 4:36:22 AM
Comment:
give me some more examples,
and tell it benefits,Where we r using..


please give me clear idea about these Article. mail me
(shashimalraj@hotmail.com)
Title: Real Boxing   
Name: Satish Dasari
Date: 3/5/2008 11:52:23 AM
Comment:
Excellent
Title: Clarity on the Basic   
Name: B Srinivasan
Date: 12/27/2007 1:11:15 PM
Comment:
Good description with the sample to explain the Boxing concept. Its worth for the beginner/new to this .NET feature
Title: Boxing & Unboxing   
Name: saleem
Date: 12/20/2007 3:41:19 PM
Comment:
-give me some more examples,
and tell it benefits.
-Why we are using boxing and unboxing. what is the use. where
we are using this concept. can u say.

please give me clear idea about these Article. mail me @ (saleem.mas@gmail.com)
Title: Good Job   
Name: Harry
Date: 12/5/2007 6:58:43 AM
Comment:
Nice example. ;-)
Keep writing.
Title: use less article   
Name: sameer
Date: 10/9/2007 8:44:05 AM
Comment:
useless article doenst make sense to me at all
Title: Keep up the good work   
Name: Rajasekhar
Date: 8/22/2007 11:34:44 AM
Comment:
Hai,

This is the correct way to explain any concept. It's really outstanding for us. Please keep writing the articles like this.

Regards - Rajasekhar.
Title: Best explanation online about this subject   
Name: Hung Dao
Date: 7/23/2007 5:53:40 PM
Comment:
I have read several online examples. All simply talks about how boxing and unboxing work but do not really show behind the scene. Keep it up your great work.
Title: nice very good examples are given But   
Name: suyog kale(suyog.kale@gmail.com)
Date: 6/8/2007 5:36:24 AM
Comment:
give me some more examples,
and tell it benefits
Title: Boxing   
Name: shiva
Date: 5/31/2007 3:24:33 AM
Comment:
nice very good examples are given
Title: boxing   
Name: velavan
Date: 4/19/2007 7:03:44 AM
Comment:
very good
Title: About boxing and unboxing   
Name: sathyanarayanan. c
Date: 3/24/2007 7:30:47 PM
Comment:
Why we are using boxing and unboxing. what is the use. where we are using this concept. can u say.
Title: Nice   
Name: Bhupender
Date: 3/22/2007 6:21:45 AM
Comment:
Its Nice, But want some more examples ...
Title: Nice   
Name: Meenu
Date: 2/19/2007 5:44:16 AM
Comment:
Its really nice..Easily understandable..
Well done..
Title: Boxing when calling methods   
Name: ad
Date: 2/9/2007 8:20:36 AM
Comment:
Suppose we have three methods:
- Boxing::CheckBoxingInt(int32)
- Boxing::CheckBoxingObject(object)
- Boxing::CheckBoxingValueType(ValueType)

Boxing (see *) is done when calling CheckBoxingObject() and CheckBoxingValueType(), but not when calling CheckBoxingInt()...

Is this correct, or?

ldarg.0
ldloc.0
call instance void Boxing::CheckBoxingInt(int32)

ldarg.0
ldloc.0
* box [mscorlib]System.Int32
call instance void Boxing::CheckBoxingObject(object)

ldarg.0
ldloc.0
* box [mscorlib]System.Int32
call instance void Boxing::CheckBoxingValueType(class [mscorlib]System.ValueType)
Title: Fine Article   
Name: sonj
Date: 2/8/2007 10:04:03 AM
Comment:
Thanks for directing the Developers
Title: Better method   
Name: prashant kumar singh
Date: 2/4/2007 9:31:19 AM
Comment:
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Title: Very Nice   
Name: kiran
Date: 12/22/2006 2:40:58 PM
Comment:
Please try some more......Help
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Date: 12/15/2006 5:35:52 AM
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Date: 10/18/2006 7:27:40 PM
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Date: 9/11/2006 10:55:39 PM
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Name: udit
Date: 9/9/2006 3:43:47 AM
Comment:
the information is given by u regarding boxing & unboxing
it cleare my doubt thanks.keep in touch.
Title: Good Example   
Name: Anoop
Date: 9/9/2006 3:43:17 AM
Comment:
Good Example keep it up
Title: Keep it up   
Name: Manish
Date: 9/8/2006 3:21:08 AM
Comment:
Good, Carry on with ur work
Title: Well Done   
Name: Anita Acharya
Date: 9/7/2006 11:50:20 PM
Comment:
U have chosen a new hobby in ur life.Best of luck & God Bless U.
Title: Keep it up   
Name: prashant
Date: 9/7/2006 9:14:58 AM
Comment:
Good....
Carry on with u r work.






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