In this article, I will try to explain sealed class and sealed method in a very simple way.
C# 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:
- A class, which restricts inheritance for security reason is declared sealed class.
- Sealed class is the last class in the hierarchy.
- Sealed class can be a derived class but can't be a base class.
- 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();
}
}
}
C# Sealed Methods
Sealed method is used to define the overriding level of a virtual method.
Sealed keyword is always used with override keyword.
Practical demonstration of sealed method.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace sealed_method
{
class Program
{
public class BaseClass
{
public virtual void Display()
{
Console.WriteLine("Virtual method");
}
}
public class DerivedClass : BaseClass
{
// Now the display method have been sealed and can;t be overridden
public override sealed void Display()
{
Console.WriteLine("Sealed method");
}
}
//public class ThirdClass : DerivedClass
//{
// public override void Display()
// {
// Console.WriteLine("Here we try again to override display method which is not possible and will give error");
// }
//}
static void Main(string[] args)
{
DerivedClass ob1 = new DerivedClass();
ob1.Display();
Console.ReadLine();
}
}
}
Hope this article will give you better view of sealed class and sealed method. Waiting! for your valuable feedback.