When to use abstract vs concrete in C Sharp (C#) - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract class in C#.

C Sharp (C#)

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

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Astatic

Bconcrete

Csealed

Dabstract

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'concrete' instead of 'abstract' to declare an abstract class.

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

2fill in blank

medium

Complete the code to create a concrete class that inherits from an abstract class.

C Sharp (C#)

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

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ASpeak

BRun

CJump

DBark

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist in the abstract class.

The concrete class Dog must override the abstract method Speak from the base class.

3fill in blank

hard

Fix the error in the code by choosing the correct keyword for the class.

C Sharp (C#)

public [1] class Vehicle {
    public void Start() {
        Console.WriteLine("Starting vehicle");
    }
}

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Asealed

Bconcrete

Cabstract

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'abstract' when the class has no abstract members.

The class is intended to be a concrete class that cannot be inherited, so sealed is the correct keyword.

4fill in blank

hard

Fill both blanks to define an abstract method and a concrete method in an abstract class.

C Sharp (C#)

public abstract class Shape {
    public abstract double [1]();
    public double [2]() {
        return 0;
    }
}

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AArea

BPerimeter

CDraw

DCalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to make a concrete method abstract or vice versa.

The abstract method Area must be implemented by subclasses, while Perimeter is a concrete method with a default implementation.

5fill in blank

hard

Fill all three blanks to create a concrete class that implements abstract methods and adds a new method.

C Sharp (C#)

public class Circle : Shape {
    public override double [1]() {
        return 3.14 * radius * radius;
    }
    public override double [2]() {
        return 2 * 3.14 * radius;
    }
    public double [3]() {
        return radius;
    }
    private double radius;
    public Circle(double r) {
        radius = r;
    }
}

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AArea

BPerimeter

CGetRadius

DCalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Not overriding all abstract methods or using wrong method names.

The class Circle overrides the abstract methods Area and Perimeter from Shape and adds a new method GetRadius.