Boxing and unboxing execution in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is boxing in C#?

Boxing is the process of converting a value type (like int) to an object type. It wraps the value inside an object so it can be treated as a reference type.

beginner

What is unboxing in C#?

Unboxing is the process of extracting the value type from the object. It converts the object back to the original value type.

intermediate

Why does boxing affect performance?

Boxing creates a new object on the heap and copies the value. This uses extra memory and CPU time, so it can slow down the program if done often.

beginner

Show a simple example of boxing and unboxing in C#.

int num = 123; // value type object obj = num; // boxing int num2 = (int)obj; // unboxing

intermediate

What happens if you unbox to the wrong type?

An InvalidCastException is thrown at runtime because the object does not contain the expected value type.

What does boxing do in C#?

A Deletes a value type

B Converts an object to a value type

C Copies an object to another object

D Converts a value type to an object

Boxing wraps a value type inside an object so it can be treated as a reference type.

Which of these is true about unboxing?

A It converts a value type to a string

B It converts an object back to a value type

C It creates a new object on the heap

D It copies a value type to another value type

Unboxing extracts the original value type from the boxed object.

What error occurs if you unbox to the wrong type?

A InvalidCastException

B NullReferenceException

C IndexOutOfRangeException

D ArgumentException

Unboxing to the wrong type throws an InvalidCastException at runtime.

Why should you avoid excessive boxing?

A It slows down performance and uses more memory

B It causes syntax errors

C It deletes variables

D It makes code unreadable

Boxing creates new objects and copies values, which uses extra memory and CPU time.

Which of these is an example of boxing?

A string s = "hello";

B int x = (int)obj;

C object obj = 10;

D int y = 5 + 3;

Assigning a value type (int 10) to an object variable causes boxing.

Explain boxing and unboxing in your own words and why they matter in C#.

Think about how value types and objects are different.

Describe a simple C# code example that shows boxing and unboxing.

Use int and object types.