Is-a relationship mental model in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method call in inheritance

What is the output of the following C# code that demonstrates the is-a relationship using inheritance?

C Sharp (C#)

class Animal {
    public virtual string Speak() {
        return "Animal sound";
    }
}

class Dog : Animal {
    public override string Speak() {
        return "Bark";
    }
}

class Program {
    static void Main() {
        Animal myPet = new Dog();
        System.Console.WriteLine(myPet.Speak());
    }
}

A Bark

B Compile-time error

C Runtime exception

D Animal sound

💡 Hint

Think about which method is called when a derived class overrides a base class method.

The variable myPet is of type Animal but refers to an instance of Dog. Because Speak() is overridden in Dog, the Dog's Speak() method is called, printing "Bark".

🧠 Conceptual

intermediate

Understanding the is-a relationship

Which statement best describes the is-a relationship in object-oriented programming?

A A class creates instances of other classes.

B A class contains another class as a member variable.

C A class implements multiple unrelated interfaces.

D A class inherits from another class, meaning it is a specialized type of that class.

💡 Hint

Think about inheritance and how one class relates to another as a type.

The is-a relationship means one class is a subtype of another through inheritance, showing a specialized version of the base class.

❓ Predict Output

advanced

Output with casting and is-a relationship

What will be the output of this C# program that uses casting and the is-a relationship?

C Sharp (C#)

class Vehicle {
    public virtual string Describe() => "Vehicle";
}

class Car : Vehicle {
    public override string Describe() => "Car";
}

class Program {
    static void Main() {
        Vehicle v = new Car();
        if (v is Car) {
            Car c = (Car)v;
            System.Console.WriteLine(c.Describe());
        } else {
            System.Console.WriteLine(v.Describe());
        }
    }
}

A Vehicle

B Invalid cast exception

C Car

D Compile-time error

💡 Hint

Check the type of the object before casting and which Describe method is called.

The variable v refers to a Car object, so the 'is' check passes. Casting to Car is safe, and the Car's Describe method returns "Car".

❓ Predict Output

advanced

Output of method hiding vs overriding

What is the output of this C# code demonstrating method hiding and the is-a relationship?

C Sharp (C#)

class Base {
    public string Show() => "Base Show";
}

class Derived : Base {
    public new string Show() => "Derived Show";
}

class Program {
    static void Main() {
        Base obj = new Derived();
        System.Console.WriteLine(obj.Show());
    }
}

A Runtime exception

B Base Show

C Compile-time error

D Derived Show

💡 Hint

Consider that method hiding does not override the base method.

The variable obj is of type Base, so the Base's Show method is called, even though the object is Derived. The new keyword hides the method but does not override it.

🧠 Conceptual

expert

Is-a relationship and interface implementation

Which statement correctly explains the is-a relationship when a class implements an interface in C#?

A Implementing an interface means the class is a subtype of the interface, establishing an is-a relationship.

B Implementing an interface creates a has-a relationship, not is-a.

C Interfaces cannot express is-a relationships in C#.

D A class implementing an interface must inherit from a base class to have an is-a relationship.

💡 Hint

Think about how interfaces define a contract that the class agrees to fulfill.

When a class implements an interface, it is considered a subtype of that interface, so it has an is-a relationship with the interface type.