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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a sealed class named 'Vehicle'.

C Sharp (C#)

public [1] class Vehicle
{
    public void Start() { }
}

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

Asealed

Babstract

Cstatic

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using 'static' which makes the class static, not sealed.

The keyword sealed prevents other classes from inheriting from this class.

2fill in blank

medium

Complete the code to prevent overriding of the 'Drive' method in derived classes.

C Sharp (C#)

public class Car
{
    public virtual void Drive() { }
}

public class SportsCar : Car
{
    public [1] override void Drive() { }
}

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

Aabstract

Bsealed

Cstatic

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' which requires the method to be overridden.

Using 'virtual' which allows overriding.

The sealed keyword on an override method stops further overriding in subclasses.

3fill in blank

hard

Fix the error in the code by completing the class declaration to prevent inheritance.

C Sharp (C#)

public class BaseClass { }

public [1] class DerivedClass : BaseClass { }

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

Astatic

Babstract

Csealed

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' which allows inheritance.

Using 'virtual' which is invalid on classes.

Marking 'DerivedClass' as sealed prevents other classes from inheriting from it.

4fill in blank

hard

Fill both blanks to declare a sealed class and a sealed override method.

C Sharp (C#)

public class Animal
{
    public virtual void Speak() { }
}

public [1] class Dog : Animal
{
    public [2] override void Speak() { }
}

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

Asealed

Babstract

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' instead of 'sealed' for the class.

Using 'virtual' instead of 'sealed' for the method.

The class 'Dog' is sealed to prevent inheritance, and the 'Speak' method in 'Dog' is sealed to prevent further overrides.

5fill in blank

hard

Fill all three blanks to create a sealed class, a sealed override method, and call the base method.

C Sharp (C#)

public class Shape
{
    public virtual void Draw() { Console.WriteLine("Drawing shape"); }
}

public [1] class Circle : Shape
{
    public [2] override void Draw()
    {
        base.[3]();
        Console.WriteLine("Drawing circle");
    }
}

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

Asealed

BDraw

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Not sealing the class or method properly.

Calling a wrong base method name.

The class 'Circle' is sealed to prevent inheritance. The 'Draw' method in 'Circle' is sealed to prevent further overrides. The base method 'Draw' is called inside the override.