Sealed Class

Sealed class is a class that cannot be inherited by any class but can be instantiated. It is often used to encapsulate a logic that needs to be used across the program but without any alteration to it. In order to declare a sealed class we need to used Sealed keyword before class.

Syntax
sealed class className {
    //Fields and methods
}

CODE

EG 1 . Creating a class called sampleClass and inheriting a sealed class Rectangle to it.

sealed class Rectangle {
    public double length, width;
    public double Area() {
        return length * width;
    }
}

class sampleClass : Rectangle {

}

CODE EXPLANATION
In the above code, we created a sealed class called Rectangle. We inherited that sealed class to sampleClass. If we write above code in visual studio, system will throw a compile time error stating 'sampleClass' : cannot derive from sealed type 'Rectangle' which means sealed class cannot be inherited by any class.


Where to use Sealed class?
Sealed classes are used to restrict the users from inheriting the class.
Imagine you are creating a class, you going to share that class to you colleague. You colleague may create a new class where he can inherit the class what you created but you don't want your class to be inherited by any other class. In this case we can use Sealed class so that it cannot be inherited by any class.