C# Abstract Class

In C#, an abstract class is a class that cannot be instantiated directly. It is used as a base class for other classes, and can contain both abstract and non-abstract methods. Abstract methods are methods that are declared but do not contain an implementation.

Declaring an Abstract Class

To declare an abstract class in C#, use the abstract keyword in the class declaration. The class can contain one or more abstract methods, as well as non-abstract methods.

1abstract class Shape
2{
3    // Abstract method
4    public abstract void Draw();
5
6    // Non-abstract method
7    public void Resize()
8    {
9        Console.WriteLine("Resizing...");
10    }
11}

Implementing an Abstract Class

To implement an abstract class in C#, you must create a derived class that inherits from the abstract class. The derived class must provide an implementation for all abstract methods declared in the abstract class.

1class Circle : Shape
2{
3    public override void Draw()
4    {
5        Console.WriteLine("Drawing a circle");
6    }
7}
8
9class Rectangle : Shape
10{
11    public override void Draw()
12    {
13        Console.WriteLine("Drawing a rectangle");
14    }
15}

Creating an Object from a Derived Class

You cannot create an object directly from an abstract class, but you can create an object from a derived class that implements the abstract class.

1Shape shape1 = new Circle();
2Shape shape2 = new Rectangle();

Benefits of Abstract Classes

Abstract classes allow you to create a hierarchy of classes that share common functionality. They also provide a level of abstraction, allowing you to create a base class that defines the interface for a set of derived classes. This can help to make your code more modular and easier to maintain.