Abstract Classes in C#

What are Abstract Classes in C#?

An abstract class in C# is a class that cannot be instantiated directly. It serves as a blueprint for other classes and may contain both abstract (unimplemented) and non-abstract (implemented) methods.

Key Features of Abstract Classes

• Cannot be instantiated directly.
• May contain abstract methods (methods without implementation).
• Can have constructors, fields, properties, and implemented methods.
• Must be inherited by derived classes, which must provide implementations for abstract methods.

Example of an Abstract Class

Below is an example of an abstract class with an abstract method that must be implemented by derived classes.

Example of an Abstract Class:

abstract class Animal
{
    // Abstract method (must be implemented in derived classes)
    public abstract void MakeSound();

    // Regular method with implementation
    public void Sleep()
    {
        Console.WriteLine("Sleeping...");
    }
}

// Derived class implementing the abstract method
class Dog : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("Bark! Bark!");
    }
}

// Usage
Dog myDog = new Dog();
myDog.MakeSound(); // Output: Bark! Bark!
myDog.Sleep();     // Output: Sleeping...
        

In this example, Animal is an abstract class with an abstract method MakeSound(). The Dog class implements this method.

Abstract Classes vs Interfaces

When to Use Abstract Classes?

• When you want to provide some default implementation while enforcing derived classes to implement specific methods.
• When objects share common behavior but also require individual implementations for some methods.
• When working with class hierarchies that require base functionality.