Abstract Class in C#

In c#, Abstract class is a class that can not be instantiated on its own

• In c#, Abstract class is a class that can not be instantiated on its own
• It is typically used as a base class for other class.
• Abstract class provides a way to achieve abstraction, because there you can just declare the methods (abstract methods) and implement them later.
• It can contain both abstract methods (methods without implementation details) and non-abstract methods (method with implementation details).
• Similar goal can be achieved with interface, but in abstract class you can also define non-abstract method. These methods are needed when you need to share some common functionality.

public abstract class Shape
{
 // it is the basic syntax of abstract class
}

Example:

abstract class Shape
{
 public abstract void Draw(); // Abstract method without implementation

    public void Display()  //non abstract method
    {
        Console.WriteLine("Displaying shape...");
    }

}

// concrete class
class Circle : Shape
{
 public override void Draw()
 {
 Console.WriteLine("Drawing a circle");
 }
}

// concrete class
class Square : Shape
{
 public override void Draw()
 {
 Console.WriteLine("Drawing a square");
 }
}

class Program
{
    static void Main()
    {
        Shape circle = new Circle();
        circle.Draw(); // Drawing a circle
        circle.Display(); //Displaying shape...

        Shape square = new Square();
        square.Draw();  // Drawing a square
        square.Display(); //Displaying shape...

    }

}

• Shape is an abstract class, which contains an abstract method Draw() and non-abstract method Display().
• We are defining high level overview of any shape. Whatever shape we will have, it must have a feature Draw. Since we don’t know the details of the shape yet (it may be circle, pentagon, rectangle) , we can not define it it advance. Circle/Rectangle/Pentagon will have it’s own draw method. That’s why Draw() method is marked as abstract-method. It’s implementation will be defined later.
• Now we have two class Circle and Square. Each class will inherit the Shape class and override the Draw() method.

Originally posted by Ravindra Devrani on February 8, 2024.

Canonical link

Exported from Medium on February 19, 2025.