What are sealed classes and sealed methods

Sealed Class

 

Sealed class is used to define the inheritance level of a class.

 

The sealed modifier is used to prevent derivation from a class. An error occurs if a sealed class is specified as the base class of another class.

 

Some points to remember:  

1.  A class, which restricts inheritance for security reason is declared, sealed class.
2.  Sealed class is the last class in the hierarchy.
3.  Sealed class can be a derived class but can't be a base class.
4.  A sealed class cannot also be an abstract class. Because abstract class has to provide functionality and here we are
     restricting it to inherit.

Practical demonstration of sealed class

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace sealed_class

{

    class Program

    {

        public sealed class BaseClass

        {

            public void Display()

        {

            Console.WriteLine("This is a sealed class which can;t be further inherited");

        }

    }

 

        public class Derived : BaseClass

        {

            // this Derived class can;t inherit BaseClass because it is sealed

        }

   

        static void Main(string[] args)

        {

            BaseClass obj = new BaseClass();

 

            obj.Display();

 

            Console.ReadLine();

        }

    }

}

 

Sealed Methods

 

Sealed method is used to define the overriding level of a virtual method.

 

Sealed keyword is always used with override keyword.

 

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