Abstract classes and methods in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract class named Animal.

C Sharp (C#)

public [1] class Animal {
    public abstract void Speak();
}

Drag options to blanks, or click blank then click option'

Asealed

Babstract

Cstatic

Dpartial

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sealed' instead of 'abstract' which prevents inheritance.

Using 'static' which makes the class non-instantiable and non-inheritable.

The keyword abstract is used to declare an abstract class in C#.

2fill in blank

medium

Complete the code to declare an abstract method Speak inside the abstract class Animal.

C Sharp (C#)

public abstract class Animal {
    public [1] void Speak();
}

Drag options to blanks, or click blank then click option'

Aoverride

Bvirtual

Cabstract

Dsealed

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'virtual' which requires a method body.

Using 'override' which is for overriding base class methods.

The abstract keyword declares a method without implementation inside an abstract class.

3fill in blank

hard

Fix the error in the derived class Dog that does not implement the abstract method Speak.

C Sharp (C#)

public class Dog : Animal {
    public [1] void Speak() {
        Console.WriteLine("Woof!");
    }
}

Drag options to blanks, or click blank then click option'

Aoverride

Babstract

Csealed

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' in the derived class method which is not allowed.

Using 'virtual' which does not fulfill the abstract method requirement.

The derived class must use override to implement the abstract method from the base class.

4fill in blank

hard

Fill both blanks to declare an abstract class Vehicle and an abstract method Move.

C Sharp (C#)

public [1] class Vehicle {
    public [2] void Move();
}

Drag options to blanks, or click blank then click option'

Aabstract

Bvirtual

Dsealed

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'virtual' for the method without a body causes a syntax error.

Using 'sealed' for the class prevents inheritance.

The class must be declared abstract and the method abstract to be incomplete and require implementation in derived classes.

5fill in blank

hard

Fill all three blanks to implement an abstract class Shape with an abstract method Area and a derived class Circle overriding Area.

C Sharp (C#)

public [1] class Shape {
    public [2] double Area();
}

public class Circle : Shape {
    private double radius;
    public Circle(double r) { radius = r; }
    public [3] double Area() {
        return Math.PI * radius * radius;
    }
}

Drag options to blanks, or click blank then click option'

Aabstract

Coverride

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Not using 'override' in the derived class method causes a compile error.

Using 'virtual' instead of 'abstract' for the base method without a body.

The class Shape and its method Area are declared abstract. The Circle class overrides the Area method to provide implementation.