C# Boxing And Unboxing Of Value Types

Front 1

What is the function of 'boxing'?

Back 1

To convert value types to reference types.

Hint 1

Add value to a box.

Front 2

What is a reference type?

Back 2

A reference type is variable that stores a reference to a location (similar to an address) that stores the actual data.

Hint 2

You're cute. What's your address?

Front 3

Show a simple example of boxing an integer type.

Back 3

long myLong = 3;
...

object myObj = myLong; //implicit boxing of myLong.

Front 4

True or False. Unboxing requires an explicit cast.

Back 4

True.
int myFoo = 3, myBar;
object myObj = myFoo;

//Following won't compile.
myBar = myObj;

//Following compiles
myBar = (int) myObj;

Front 5

Will this code snippet compile?
int myBar = 3;

object myObj = myBar;

int k = (short) myObj;

Back 5

No.

//Following gives InvalidCastException
k = (short) myObj;

Although there is an implicit cast from short to int even an explicit cast is not allowed during an unboxing operation.

Front 6

Which of these statements is a valid boxing operation?

int myFoo;
object myObj;
object yourObj = 4;

a. myObj = myFoo;
b. myFoo = 3; myObj = myFoo;
c. myObj = yourObj;
d. myObj = 4;

Back 6

b and d. In statement d, the literal '4' gets boxed into myObj. myObj can the be unboxed into any appropriate integer variable.