Boxing and unboxing execution in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to box the integer value into an object.

C Sharp (C#)

int num = 10;
object boxedNum = [1];

Drag options to blanks, or click blank then click option'

Anum.ToString()

B(object)num

CConvert.ToObject(num)

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using ToString() instead of boxing.

Trying to use Convert.ToObject which does not exist.

Boxing is done by converting the value type to object explicitly or implicitly. Here, casting num to object boxes it.

2fill in blank

medium

Complete the code to unbox the object back to an integer.

C Sharp (C#)

object boxedNum = 20;
int unboxedNum = [1];

Drag options to blanks, or click blank then click option'

A(int)boxedNum

BConvert.ToInt32(boxedNum)

CboxedNum as int

Dint.Parse(boxedNum.ToString())

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as int' which returns null for value types.

Using Convert.ToInt32 which works but is not unboxing.

Unboxing requires an explicit cast from object to the original value type. Using (int)boxedNum correctly unboxes the value.

3fill in blank

hard

Fix the error in the unboxing code to avoid InvalidCastException.

C Sharp (C#)

object boxedValue = 15;
long unboxedValue = [1];

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A(long)(int)boxedValue

B(long)boxedValue

C(int)boxedValue

DConvert.ToInt64(boxedValue)

Attempts:

3 left

💡 Hint

Common Mistakes

Casting directly to long causes InvalidCastException.

Using Convert.ToInt64 does not unbox but converts.

The object holds an int, so unboxing must first cast to int, then convert to long. Direct cast to long causes an error.

4fill in blank

hard

Fill both blanks to create a dictionary with boxed integers and unbox them safely.

C Sharp (C#)

var dict = new Dictionary<string, object> {
    {"one", [1],
    {"two", [2]
};

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A1

B"two"

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using string values instead of integers for values.

Using non-string keys.

The dictionary stores values as objects, so integers 1 and 2 are boxed automatically when added.

5fill in blank

hard

Fill all three blanks to unbox values from the dictionary and sum them.

C Sharp (C#)

var dict = new Dictionary<string, object> {
    {"a", 5},
    {"b", 10}
};
int sum = (int)dict[[1]] + (int)dict[[2]] + [3];

Drag options to blanks, or click blank then click option'

A"a"

B"b"

C0

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using integer keys instead of string keys.

Adding a wrong number instead of zero.

Access dictionary values by their string keys and unbox them to int. Adding 0 completes the sum correctly.