Object instantiation with new 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 Person {
    public string Name;
    public Person(string name) {
        Name = name;
    }
}

Person p = new Person("Alice");
Console.WriteLine(p.Name);

A Compilation error

B null

C Person

D Alice

💡 Hint

Look at how the constructor sets the Name property.

The constructor assigns the string "Alice" to the Name field. So printing p.Name outputs "Alice".

❓ Predict Output

intermediate

What happens when you instantiate a class without a constructor?

What will be the output of this code?

C Sharp (C#)

class Box {
    public int Width = 5;
}

Box b = new Box();
Console.WriteLine(b.Width);

A 0

B NullReferenceException

C 5

D Compilation error

💡 Hint

Fields with initial values keep those values even without a constructor.

The Width field is initialized to 5 directly. So when the object is created, Width is 5.

❓ Predict Output

advanced

What is the output of this code with multiple constructors?

What will this program print?

C Sharp (C#)

class Car {
    public string Model;
    public int Year;

    public Car() {
        Model = "Unknown";
        Year = 0;
    }

    public Car(string model, int year) {
        Model = model;
        Year = year;
    }
}

Car car = new Car("Tesla", 2023);
Console.WriteLine($"{car.Model} {car.Year}");

A Unknown 0

B Tesla 2023

C Tesla 0

D Compilation error

💡 Hint

Which constructor is called depends on the parameters passed with new.

The constructor with parameters is called, setting Model to "Tesla" and Year to 2023.

❓ Predict Output

advanced

What error does this code raise?

What happens when you run this code?

C Sharp (C#)

class Animal {
    public string Name;
}

Animal a = new Animal();
Console.WriteLine(a.Name.Length);

A NullReferenceException

B 0

C Compilation error

D Empty string printed

💡 Hint

Name is not initialized, so it is null by default.

The Name field is null by default. Accessing Length on null causes NullReferenceException.

🧠 Conceptual

expert

How many objects are created here?

How many objects are created in memory after running this code?

C Sharp (C#)

class Node {
    public Node Next;
}

Node first = new Node();
first.Next = new Node();

A 2

B 1

C 0

D 3

💡 Hint

Each 'new' keyword creates one object.

Two 'new' keywords create two separate Node objects in memory.