C# Sealed Class and Method

In C#, the sealed keyword is used to restrict inheritance from a class or to prevent further modification of a method within a derived class. A sealed class or method cannot be inherited or overridden by any other class or method.

Sealed Class

A sealed class in C# is a class that cannot be inherited by any other class. This means that you cannot create a derived class from a sealed class.

1sealed class Vehicle
2{
3    // class members
4}
5
6class Car : Vehicle // Error: Cannot derive from sealed type 'Vehicle'
7{
8    // class members
9}

Sealed Method

A sealed method in C# is a method that cannot be overridden by any derived class. This means that you cannot change the implementation of a sealed method in any derived class.

1class Vehicle
2{
3    public virtual void Start()
4    {
5        Console.WriteLine("Vehicle started.");
6    }
7}
8
9class Car : Vehicle
10{
11    public sealed override void Start()
12    {
13        Console.WriteLine("Car started.");
14    }
15}
16
17class SportsCar : Car // Error: Cannot override sealed method 'Car.Start()'
18{
19    // class members
20}