What is a sealed class in C#?

Classes can be defined as data types that are user-defined, representing the state (properties) and the behavior (actions) of an object.

Types of classes

Classes have four major types in C#, which are as follows.

  1. Abstract class
  2. Partial class
  3. Sealed class
  4. Static class
Types of classes in C#
Types of classes in C#

In this Answer, we’ll only discuss the sealed class.

Sealed class

A type of class that cannot be inherited into any other class and has restricted access to its properties is called a Sealed class.

The main purpose of the sealed class is to restrict the inheritance feature from the class user, i.e., the sealed class cannot be used to generate a derived class. Sealed class can be generated using the sealed keyword.

Example

namespace SealedClass {
  sealed class Car {
    
  }
  // trying to inherit sealed class
  // Error Code
  class BMW : Car{
    
  }   
  class Program  {
    static void Main (string [] args) {
      // create an object of BMW class
      BMW mycar = new BMW();  
    }
  }
}

Explanation

In the above code, the "SealedClass.BMW": cannot derive from sealed type "SealedClass.Car" is generated, showcasing that we cannot generate a derived class from a sealed class.

  • Line 2: We declare a class of sealed type using a sealed keyword.
  • Line 8: We try to write a derived class BMW : Car, and this line generates an error.
  • Line 12–20: This contains the main program that creates an object of derived class BMW.

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