In the C#, Sealed classes are used to restrict the users from inheriting the class. A class can be sealed by using the sealed keyword.
C# sealed keyword applies restrictions on the class and method. If we create a sealed class, it cannot be derived. If we create a sealed method, it cannot be overridden.
C# Sealed class
using System;
sealed public class Animal{
public void eat() { Console.WriteLine("eating..."); }
}
public class Cat: Animal
{
public void bark() { Console.WriteLine("barking..."); }
}
public class SealedExample
{
public static void Main()
{
Cat objCat = new Cat();
objCat.eat();
objCat.bark();
}
}
Output
Compilation error (line 5, col 14): 'Cat': cannot derive from sealed type 'Animal'
C# Sealed method
using System;
public class Animal{
public virtual void eat() { Console.WriteLine("eating..."); }
public virtual void run() { Console.WriteLine("running..."); }
}
public class Cat: Animal
{
public override void eat() { Console.WriteLine("eating bread..."); }
public sealed override void run() {
Console.WriteLine("running very fast...");
}
}
public class BabyCat: Cat
{
public override void eat() { Console.WriteLine("eating biscuits..."); }
public override void run() { Console.WriteLine("running slowly..."); }
}
public class TestSealed
{
public static void Main()
{
BabyCat obj = new BabyCat();
obj.eat();
obj.run();
}
}
Output
Compilation error (line 17, col 26): 'BabyCat.run()': cannot override inherited member 'Cat.run()' because it is sealed
using System;
public class SealedExample
{
public static void Main()
{
sealed int number = 10;
number++;
Console.WriteLine(number);
}
}
Output
Compile Time Error: Invalid expression term 'sealed'