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();

Sealed Methods

Sealed method is used to define the overriding level of a virtual method.
Sealed keyword is always used with override keyword.