c#: shield class

Sealed classes are used to restrict the inheritance feature of object oriented programming. Once a class is defined as sealed class, this class cannot be inherited. 
In C#, the sealed modifier is used to define a class as sealed. In Visual Basic .NET,NotInheritable keyword serves the purpose of sealed. If a class is derived from a sealed class, compiler throws an error. 
If you have ever noticed, structs are sealed. You cannot derive a class from a struct.  
The following class definition defines a sealed class in C#: 

// Sealed class

sealed class SealedClass

{

    } 

In the following code, I create a sealed class SealedClass and use it from Class1. If you run this code, it will work fine. But if you try to derive a class from sealed class, you will get an error.

using System;

class Class1

{

    static void Main(string[] args)

    {

        SealedClass sealedCls = new SealedClass();

        int total = sealedCls.Add(4, 5);

        Console.WriteLine("Total = " + total.ToString());

    }

}

// Sealed class

sealed class SealedClass

{

    public int Add(int x, int y)

    {

        return x + y;

    }

}