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Boxing in C# vs. Unboxing in C#: What's the Difference?

Edited by Huma Saeed || By Sumera Saeed || Published on February 7, 2024
Boxing in C# is converting a value type to an object type, while unboxing is converting an object type back to a value type.

Key Differences

Boxing in C# is the process of converting a value type (like int or double) into an object type. This is done implicitly by the C# runtime, encapsulating the value type inside an object on the heap. Unboxing, conversely, is the explicit conversion of an object type back to a value type. It extracts the value type from the object, reverting it to its original stack-based form.
Sumera Saeed
Feb 07, 2024
When boxing, a value type is wrapped within a System.Object, which involves a memory allocation on the heap. This can lead to performance overhead due to the additional memory management required. Unboxing, on the other hand, requires the object to be explicitly cast back to the original value type, which involves checking the compatibility of the object with the value type, adding a small computational overhead.
Huma Saeed
Feb 07, 2024
Boxing is often used in scenarios where value types need to be passed to methods expecting an object, or stored in data structures that hold objects. It provides a way to treat value types as reference types. In contrast, unboxing is used when the stored value needs to be retrieved in its original type, typically when interacting with generic collections or APIs that return objects.
Sumera Saeed
Feb 07, 2024
A key aspect of boxing is that it creates a new object, leading to a disconnection between the original value type and the boxed object. Changes made to the boxed object do not affect the original value. Conversely, when unboxing, the extracted value is a direct copy of the data in the object, allowing modifications to the unboxed value without affecting the boxed object.
Janet White
Feb 07, 2024
Boxing in C# can be seen as a type safety feature, ensuring that value types can be used in a polymorphic way with reference types. However, unboxing requires careful handling to avoid errors such as InvalidCastException, which occur if the object is not of the expected value type.
Harlon Moss
Feb 07, 2024
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Comparison Chart

Process

Conversion from value to object type
Conversion from object to value type
Sumera Saeed
Feb 07, 2024

Memory Allocation

Allocates memory on the heap
No new memory allocation
Sumera Saeed
Feb 07, 2024

Usage Scenario

When value types need to be treated as reference types
When retrieving original value type from an object
Sumera Saeed
Feb 07, 2024

Type Safety

Implicit conversion; type-safe
Requires explicit casting; prone to casting errors
Harlon Moss
Feb 07, 2024

Performance Impact

Can increase due to heap allocation
Can decrease due to type-checking overhead
Janet White
Feb 07, 2024
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Boxing in C# and Unboxing in C# Definitions

Boxing in C#

Boxing is wrapping a value type in an object type in C#.
Int i = 123; object o = i; // Boxing
Sumera Saeed
Jan 24, 2024

Unboxing in C#

Unboxing in C# is casting an object back to a specific value type.
Object obj = 3.14; double d = (double)obj; // Unboxing
Sumera Saeed
Jan 24, 2024

Boxing in C#

In boxing, a value type is encapsulated within a System.Object.
Object box = 10; // Boxing an integer
Sumera Saeed
Jan 24, 2024

Unboxing in C#

Unboxing is explicit conversion from object to a struct or primitive.
Object obj = 'x'; char ch = (char)obj; // Unboxing
Janet White
Jan 24, 2024

Boxing in C#

Boxing in C# occurs when a value type is assigned to an object variable.
Double d = 3.14; object obj = d; // Boxing
Janet White
Jan 24, 2024

Unboxing in C#

Unboxing extracts the value type from an object in C#.
Object o = 10; int i = (int)o; // Unboxing
Sumera Saeed
Jan 24, 2024

Boxing in C#

Boxing converts value types to object, enabling polymorphic behavior.
ArrayList list = new ArrayList(); list.Add(42); // Boxing
Huma Saeed
Jan 24, 2024

Unboxing in C#

Unboxing converts an object to its original value type form.
Object box = 42; int number = (int)box; // Unboxing
Sumera Saeed
Jan 24, 2024

Boxing in C#

Boxing is implicit conversion of structs or primitives to object type.
Char ch = 'x'; object obj = ch; // Boxing
Sumera Saeed
Jan 24, 2024

Unboxing in C#

In unboxing, a value type is retrieved from a boxed object.
ArrayList list = new ArrayList(); list.Add(10); int val = (int)list[0]; // Unboxing
Aimie Carlson
Jan 24, 2024

FAQs

Why is boxing used in C#?

To treat value types as reference types for polymorphism or storing in collections.
Sumera Saeed
Feb 07, 2024

What is boxing in C#?

Boxing is converting a value type to an object type in C#.
Sumera Saeed
Feb 07, 2024

Does boxing in C# affect performance?

Yes, it involves heap allocation and can reduce performance.
Janet White
Feb 07, 2024

When is unboxing necessary in C#?

When retrieving the original value type stored in an object.
Janet White
Feb 07, 2024

What is unboxing in C#?

Unboxing is converting an object type back to a value type in C#.
Huma Saeed
Feb 07, 2024

Is boxing in C# type-safe?

Yes, boxing is type-safe as it converts to System.Object.
Sumera Saeed
Feb 07, 2024

Does unboxing require explicit casting in C#?

Yes, unboxing always requires explicit casting.
Sumera Saeed
Feb 07, 2024

Can unboxing change the original boxed object in C#?

No, unboxing creates a copy of the value, leaving the boxed object unchanged.
Sumera Saeed
Feb 07, 2024

How can unboxing errors be avoided in C#?

By ensuring the object's type matches the expected value type.
Janet White
Feb 07, 2024

Can all objects be unboxed in C#?

Only objects that were previously boxed from a value type.
Sumera Saeed
Feb 07, 2024

Can boxing occur implicitly in C#?

Yes, it often happens implicitly when assigning value types to object variables.
Aimie Carlson
Feb 07, 2024

Can unboxing lead to InvalidCastException in C#?

Yes, if the object's type doesn't match the type being cast to.
Sumera Saeed
Feb 07, 2024

Is unboxing in C# error-prone?

Yes, incorrect casting during unboxing can lead to runtime errors.
Sumera Saeed
Feb 07, 2024

What happens to the original value during boxing in C#?

It gets copied into a new object on the heap, disconnecting from the original.
Sumera Saeed
Feb 07, 2024

How does unboxing work with generics in C#?

Generics can reduce the need for unboxing by handling specific types.
Janet White
Feb 07, 2024

Why is boxing necessary in non-generic collections in C#?

Because non-generic collections hold items as objects, requiring boxing for value types.
Janet White
Feb 07, 2024

Is it possible to avoid boxing in C#?

Yes, by using generics or avoiding assigning value types to object types.
Sumera Saeed
Feb 07, 2024

How does the .NET runtime handle boxing and unboxing?

It handles them automatically but requires careful programming to avoid performance issues.
Aimie Carlson
Feb 07, 2024

What types of data can be boxed in C#?

Any value type, including primitives and structs, can be boxed.
Aimie Carlson
Feb 07, 2024

What is the impact of boxing on memory in C#?

It increases memory usage due to additional object creation on the heap.
Aimie Carlson
Feb 07, 2024
About Author
Written by
Sumera Saeed
Sumera is an experienced content writer and editor with a niche in comparative analysis. At Diffeence Wiki, she crafts clear and unbiased comparisons to guide readers in making informed decisions. With a dedication to thorough research and quality, Sumera's work stands out in the digital realm. Off the clock, she enjoys reading and exploring diverse cultures.
Edited by
Huma Saeed
Huma is a renowned researcher acclaimed for her innovative work in Difference Wiki. Her dedication has led to key breakthroughs, establishing her prominence in academia. Her contributions continually inspire and guide her field.

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