Reference assignment and shared state in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code?

Consider the following C# code snippet. What will be printed to the console?

C Sharp (C#)

class Box {
    public int Value;
}

Box a = new Box();
a.Value = 5;
Box b = a;
b.Value = 10;
Console.WriteLine(a.Value);

A 10

B 5

C 0

D Compilation error

💡 Hint

Remember that classes are reference types in C#.

Both a and b refer to the same Box object. Changing b.Value changes a.Value as well.

❓ Predict Output

intermediate

What is the output of this code with structs?

What will this C# code print to the console?

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 5

B 1

C 0

D Compilation error

💡 Hint

Structs are value types in C#.

Assigning p1 to p2 copies the data. Changing p2.X does not affect p1.X.

🔧 Debug

advanced

Why does this code print 0 instead of 10?

Examine the code below. It is intended to print 10, but it prints 0 instead. What is the reason?

C Sharp (C#)

class Counter {
    public int Count;
}

void Increment(Counter c) {
    c = new Counter();
    c.Count = 10;
}

Counter myCounter = new Counter();
Increment(myCounter);
Console.WriteLine(myCounter.Count);

A The Counter class is a struct and is copied by value.

B The Count field is private and cannot be accessed.

C The method assigns a new object to the parameter, which does not affect the original reference.

D The method Increment is never called.

💡 Hint

Think about how reference parameters work in C#.

The parameter c is a copy of the reference. Assigning a new object to c does not change the original myCounter reference.

❓ Predict Output

advanced

What is the output of this code using ref keyword?

What will this C# code print to the console?

C Sharp (C#)

class Number {
    public int Value;
}

void Change(ref Number n) {
    n = new Number();
    n.Value = 20;
}

Number num = new Number();
num.Value = 5;
Change(ref num);
Console.WriteLine(num.Value);

A 20

B 5

C 0

D Compilation error

💡 Hint

The ref keyword allows the method to modify the caller's reference.

Using ref means the method can change the caller's variable to point to a new object.

🧠 Conceptual

expert

How many distinct objects exist after this code runs?

Consider this C# code snippet. How many distinct Person objects exist in memory after execution?

C Sharp (C#)

class Person {
    public string Name;
}

Person p1 = new Person { Name = "Alice" };
Person p2 = p1;
p2.Name = "Bob";
p2 = new Person { Name = "Charlie" };

A 1

B 3

C 0

D 2

💡 Hint

Count how many times new objects are created.

First, p1 and p2 point to the same object (Alice). Then p2 is assigned a new object (Charlie). So there are two objects: one with Name "Bob" (original) and one with Name "Charlie".