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Table of contents
Advantages of Boxing
Disadvantages of Boxing
Advantages of Unboxing
Disadvantages of Unboxing
Frequently asked questions
What's the distinction between the ref and out parameters?
What is the distinction between an array and an array list?
What is the distinction between a DLL and an EXE?
What does serialization entail?
What's the difference between object pooling and connection pooling?
Last Updated: Mar 27, 2024

Boxing and Unboxing in C#

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Prerita Agarwal
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23 Jul, 2024 @ 01:30 PM


This article will explain C# Boxing and Unboxing. In C# type system makes extensive use of the notions of boxing and Unboxing. They connect the two major data types in C#, the Value and Reference types. Although all value types are stored in the stack, they must be addressed as the heap in specific cases. Because reference types are kept in a heap, a value type can be converted to a reference type. Boxing is the term for this transformation. Boxing is the polar opposite of Unboxing.


Converting a value type to a type object or any interface type implemented by this value type is known as boxing. The common language runtime (CLR) wraps a value type in a System. Object instance and saves it on the managed heap when it boxes it—unboxing extracts the object's value type. Unboxing is more explicit than boxing. The C# unified view of the type system is based on the notion of boxing and unpacking, which allows any type value to be handled as an object.


int Val=1;
object obj=Val; //boxing

The first line establishes the Val value type and gives it one value. The second line creates an instance of the object obj and assigns Val to it. As a result, the boxing process copies the Val integer's value to the object obj. When a value type is used instead of a reference type, the compiler constructs an object box in which the value type's value is place. Both variables Val and obj are now present, but the value of obj is store in a heap. This signifies that the values are unrelated to one another. As a result, if the value of obj changes in the future, the value of Val remains unaffected. For example, the value of obj is changes, as seen below, but the value of Val remains unchanged.

int val= 256;
object obj=Val;
Console.WriteLine("Val={0}, obj={1}",Val, Obj); //Output

The value of Obj has been changed, but the value of Val has not been changed, as shown in the diagram. The data for the value type is placed directly on the stack. In contrast, the data for the Reference type is accessible indirectly through the reference variable obj, which points to the data stored in heap memory. The stack holds the reference variable obj. The reference variables in the boxing type conversion employ stack and result.

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Advantages of Boxing

When a value type transform into a Base object or an interface, boxing comes in handy. The value type is subsequently converted to a reference type by the CLR (Common Language Runtime). CLR allocates heap memory before copying the value type instance to it.

Disadvantages of Boxing

Boxing is a costly procedure since it copies an object from a stack to a heap, which takes a lot of processing cycles and heap space.

The same object can appear in two separate places in memory, each with a different state.


It is the process of converting an object type to a value type. Unboxing is the complete opposite of boxing. Unboxing is altering the type object to any value type explicitly.

Only variables that have already been boxed can be unboxed. It's crucial to understand that Unboxing necessitates an object type that has been boxed from value type to object type. The unboxing process verifies that the given value type matches the type contained in the object type. An error is a mismatch.

An unpacking operation entails determining whether the object instance is a boxed value of the specified value type and then copying the value from the instance.


object box = 12;  
int i = (int)box;  

conceptually correspond to,

object box = new int_Box(12);  
int i = ((int_Box)box).value; 

The value of the source argument must reference an object that was previously formed by boxing a value of that value-type for an unpacking conversion to that value-type to proceed at run-time. An InvalidCastException is issued if the source parameter is null or a reference to an incompatible object.

Advantages of Unboxing

Unboxing is explicit conversion. The item from the heap memory is copied to the value from the stack memory.

Disadvantages of Unboxing

We must guarantee that the value type is large enough to hold the object's value when unpacking a value. A run-time error may occur if the operation is not compile correctly.

Also read,  Ienumerable vs Iqueryable

Frequently asked questions

What's the distinction between the ref and out parameters?

A ref argument is initialized before being supplied to a method, whereas a parameter does not initialize before pass.

What is the distinction between an array and an array list?

Only elements of the same kind can be store in an array. The array's size is predetermined. An array list is identical to an array. However, it has no defined size.

What is the distinction between a DLL and an EXE?

EXE is an OUT-of-Process component, while Dll is an IN-Process component.
Exe is for one-time use only, whereas DLL can be used several times.
DLLs cannot be started as standalone executables.

What does serialization entail?

When we wish to send an item over the internet, we must first turn it into a stream of bytes. Serialization is the process of transforming an object into a stream of bytes. Serializable, an object must inherit the ISerialize Interface.
De-serialization is the process of converting a stream of bytes into an object.

What's the difference between object pooling and connection pooling?

You can manage the number of connections in object pooling. You can control the maximum number of links reached with connection pooling. If there is nothing in the pool when employing connection pooling, a connection is made because the creation is on the same thread. In object pooling, the collection decides whether or not to create an object based on whether or not the highest reaches, in which case the next available object is return. However, if the thing is hefty, this may increase the time complexity.

Also Read About - singleton design pattern in c#


This article has gone through Boxing and Unboxing. Value Types (int, char, etc. ), Reference Types (object), and Pointer Types are the three data types in the C# Type System. It essentially converts a Value Type to a Reference Type and back. Boxing and Unboxing provide a unified view of the type system, allowing any type value to be handled as an object. 
Check out the Introduction in C#. It will clear the concept.

If you want to know the Difference between Argument and Parameter check out this article.

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