Sealed vs Virtual in C#

The virtual keyword in C# indicates that a method:

• Can be overridden by a derived class

• Cannot be overridden

• Must be implemented by every subclass

• Is only accessible within the same assembly

The purpose of a virtual method is to:

• Provide a default implementation that derived classes can change

• Force all derived classes to implement the method

• Prevent inherited classes from accessing the method

• Allow only static access to the method

Which of the following keywords is used in a derived class to replace the behavior of a virtual method?

• override

• base

• extends

• implements

When overriding a method, what happens if you call base.MethodName()?

• It creates a new instance of the base class

• It calls the original implementation from the base class

• It removes the overridden implementation

• It hides the method from derived classes

Which keyword prevents further overriding of a virtual or overridden method?

• sealed

• static

• const

• readonly

What happens if a derived class tries to override a sealed method?

• The base version runs automatically

• The compiler produces an error

• The override is ignored silently

• The override only applies at runtime

The ability to override virtual methods in subclasses is an example of which object-oriented principle?

• Polymorphism

• Encapsulation

• Aggregation

• Composition

If a class is declared as sealed, what does that mean?

• It cannot be inherited from

• It cannot have private members

• It cannot be instantiated

• It cannot contain virtual methods

The override keyword must be used when:

• Writing a constructor

• Redefining a base class virtual method in a subclass

• Declaring a private field

• Implementing an interface

The virtual keyword allows a method to be __________ in a subclass.