Value types vs reference types mental model in C Sharp (C#) - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Understanding value type assignment

What is the output of this C# code snippet?

C Sharp (C#)

int a = 5;
int b = a;
b = 10;
Console.WriteLine(a);

A Compilation error

B 5

C 0

D 10

💡 Hint

Remember that integers are value types and copying creates a separate copy.

In C#, int is a value type. When b is assigned a, it copies the value. Changing b later does not affect a.

❓ Predict Output

intermediate

Reference type assignment behavior

What will this C# program print?

C Sharp (C#)

class Box { public int Size; }

Box box1 = new Box() { Size = 3 };
Box box2 = box1;
box2.Size = 7;
Console.WriteLine(box1.Size);

A 7

B 3

C 0

D Compilation error

💡 Hint

Classes are reference types; variables hold references to the same object.

Box is a class, so box1 and box2 refer to the same object. Changing box2.Size changes box1.Size as well.

🔧 Debug

advanced

Why does this struct behave unexpectedly?

Consider this C# code. What is the output and why? struct Point { public int X; public int Y; } Point p1 = new Point() { X = 1, Y = 2 }; Point p2 = p1; p2.X = 5; Console.WriteLine(p1.X);

C Sharp (C#)

struct Point { public int X; public int Y; }

Point p1 = new Point() { X = 1, Y = 2 };
Point p2 = p1;
p2.X = 5;
Console.WriteLine(p1.X);

A Compilation error

B 5

C 1

D 0

💡 Hint

Structs are value types and copying creates a new independent copy.

Point is a struct (value type). Assigning p2 = p1 copies the values. Changing p2.X does not affect p1.X.

❓ Predict Output

advanced

Effect of modifying a reference type inside a method

What will this C# code print?

C Sharp (C#)

class Container { public int Value; }

void Modify(Container c) {
  c.Value = 10;
  c = new Container() { Value = 20 };
}

Container cont = new Container() { Value = 5 };
Modify(cont);
Console.WriteLine(cont.Value);

A Compilation error

B 20

C 5

D 10

💡 Hint

The method changes the object's property, but reassigning the parameter does not affect the original reference.

The method modifies the Value property of the object cont points to, setting it to 10. Then it reassigns the parameter c to a new object, but this does not change cont outside the method.

🧠 Conceptual

expert

Memory behavior of value vs reference types

Which statement best describes how value types and reference types are stored in memory in C#?

A Value types are stored on the stack; reference types are stored on the heap with variables holding references.

B Value types are stored on the heap; reference types are stored on the stack with variables holding values.

C Both value and reference types are always stored on the heap.

D Both value and reference types are always stored on the stack.

💡 Hint

Think about where simple data and objects live in memory.

In C#, value types (like int, struct) are usually stored on the stack, which is fast and short-lived. Reference types (like class) are stored on the heap, and variables hold references (pointers) to these objects.