What Is an Abstract Class?

An abstract class in C# is a class that cannot be instantiated. It is intended to be a base class that other classes inherit from. Abstract classes can contain both abstract members (without implementation) and concrete members (with implementation).

Key Features of Abstract Classes in C#

• Cannot be instantiated directly.
• May contain abstract methods, properties, or indexers.
• Can contain fully implemented methods.
• Used to enforce a base structure for derived classes.

Example in C#

abstract class Animal
{
    public abstract void MakeSound(); // abstract method

    public void Sleep()               // normal method
    {
        Console.WriteLine("Sleeping...");
    }
}

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

In this example, Animal is an abstract class. You cannot create new Animal(), but you can create Dog, which inherits and implements the abstract method.