Sealed classes and methods in C Sharp (C#) - Mini Project: Build & Apply

Sealed Classes and Methods in C#

📖 Scenario: Imagine you are creating a simple animal classification system. You want to make sure that some animals cannot be further specialized or changed by other programmers. This is where sealed classes and methods help.

🎯 Goal: You will create a base class and a sealed class that cannot be inherited. You will also create a method that is sealed to prevent overriding. This will help you understand how to protect parts of your code from changes.

📋 What You'll Learn

Create a base class called Animal with a virtual method MakeSound() that prints a generic sound.

Create a class called Dog that inherits from Animal and overrides MakeSound() to print "Bark".

Seal the Dog class so no other class can inherit from it.

Create a class called Cat that inherits from Animal and overrides MakeSound().

Seal the MakeSound() method in Cat so it cannot be overridden further.

Create a class called PersianCat that inherits from Cat and try to override MakeSound() (this should cause an error).

💡 Why This Matters

🌍 Real World

Sealed classes and methods are used in software to protect important parts of code from accidental changes, ensuring stability and security.

💼 Career

Understanding sealed classes and methods is important for writing robust C# applications and working with frameworks that use these features to maintain code integrity.

1

Create the base class Animal

Create a public class called Animal with a public virtual method MakeSound() that prints "Some generic animal sound".

C Sharp (C#)

# Your code here

Need a hint?

Use public virtual void MakeSound() inside the Animal class to allow overriding.

2

Create and seal the Dog class

Create a public sealed class called Dog that inherits from Animal. Override the MakeSound() method to print "Bark".

C Sharp (C#)

public class Animal
{
    public virtual void MakeSound()
    {
        System.Console.WriteLine("Some generic animal sound");
    }
}

# Your code here

Need a hint?

Use the sealed keyword before class Dog to prevent inheritance.

3

Create Cat class and seal its MakeSound() method

Create a public class called Cat that inherits from Animal. Override the MakeSound() method and seal it. The method should print "Meow".

C Sharp (C#)

public class Animal
{
    public virtual void MakeSound()
    {
        System.Console.WriteLine("Some generic animal sound");
    }
}

public sealed class Dog : Animal
{
    public override void MakeSound()
    {
        System.Console.WriteLine("Bark");
    }
}

# Your code here

Need a hint?

Use sealed override before the method name to prevent further overriding.

4

Try to override sealed method in PersianCat

Create a public class called PersianCat that inherits from Cat. Try to override the MakeSound() method to print "Purr". Then create a Main method to create one Dog, one Cat, and one PersianCat object and call their MakeSound() methods.

C Sharp (C#)

public class Animal
{
    public virtual void MakeSound()
    {
        System.Console.WriteLine("Some generic animal sound");
    }
}

public sealed class Dog : Animal
{
    public override void MakeSound()
    {
        System.Console.WriteLine("Bark");
    }
}

public class Cat : Animal
{
    public sealed override void MakeSound()
    {
        System.Console.WriteLine("Meow");
    }
}

# Your code here

Need a hint?

The PersianCat class cannot override MakeSound() because it is sealed in Cat. The output will show the sounds from Dog, Cat, and PersianCat (which uses Cat's method).