Value type copying behavior in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of struct value copy

What is the output of this C# code?

struct Point { public int X; public int Y; }
Point p1 = new Point { X = 5, Y = 10 };
Point p2 = p1;
p2.X = 20;
Console.WriteLine(p1.X);

C Sharp (C#)

struct Point { public int X; public int Y; }
Point p1 = new Point { X = 5, Y = 10 };
Point p2 = p1;
p2.X = 20;
Console.WriteLine(p1.X);

A 0

B 20

C 5

D Compilation error

💡 Hint

Remember that structs are value types and copying creates a new independent copy.

In C#, structs are value types. When you assign p1 to p2, a copy of the data is made. Changing p2.X does not affect p1.X, so p1.X remains 5.

❓ Predict Output

intermediate

Effect of modifying a copied value type

Consider this code:

int a = 10;
int b = a;
b = 30;
Console.WriteLine(a);

What will be printed?

C Sharp (C#)

int a = 10;
int b = a;
b = 30;
Console.WriteLine(a);

A 30

B 10

C 0

D Compilation error

💡 Hint

int is a value type, so assignment copies the value.

Assigning b = a copies the value 10. Changing b to 30 does not affect a, so a remains 10.

❓ Predict Output

advanced

Value type in method parameter behavior

What is the output of this code?

struct Number { public int Value; }
void Change(Number n) { n.Value = 100; }
Number num = new Number { Value = 50 };
Change(num);
Console.WriteLine(num.Value);

C Sharp (C#)

struct Number { public int Value; }
void Change(Number n) { n.Value = 100; }
Number num = new Number { Value = 50 };
Change(num);
Console.WriteLine(num.Value);

A Compilation error

B 100

C 0

D 50

💡 Hint

Value types are passed by value by default.

The method Change receives a copy of num. Modifying n.Value changes only the copy, so num.Value remains 50.

❓ Predict Output

advanced

Effect of ref keyword on value type parameter

What will this code print?

struct Data { public int X; }
void Modify(ref Data d) { d.X = 99; }
Data data = new Data { X = 10 };
Modify(ref data);
Console.WriteLine(data.X);

C Sharp (C#)

struct Data { public int X; }
void Modify(ref Data d) { d.X = 99; }
Data data = new Data { X = 10 };
Modify(ref data);
Console.WriteLine(data.X);

A 99

B Compilation error

C 0

D 10

💡 Hint

The ref keyword passes the value type by reference, allowing modification.

Using ref passes the struct by reference, so changes inside Modify affect the original data. data.X becomes 99.

🧠 Conceptual

expert

Understanding boxing and value type copying

Which statement best describes what happens when a value type is boxed in C#?

A A reference type object is created on the heap containing a copy of the value type data.

B The value type is passed by reference to avoid copying.

C The original value type is converted into a reference type without copying data.

D The value type is converted into a pointer to the original data.

💡 Hint

Boxing involves creating an object on the heap.

Boxing copies the value type data into a new object on the heap, which is a reference type. This allows value types to be treated as objects.