Runtime polymorphism execution in C Sharp (C#) - Cheat Sheet & Quick Revision

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beginner

What is runtime polymorphism in C#?

Runtime polymorphism means that the method to be called is determined during program execution, not at compile time. It allows a base class reference to call derived class methods using method overriding.

beginner

How do you enable runtime polymorphism in C#?

By declaring a method in the base class as <code>virtual</code> and overriding it in the derived class using <code>override</code>. Then, calling the method through a base class reference triggers the derived class version at runtime.

beginner

What keyword is used in the base class method to allow overriding?

The <code>virtual</code> keyword marks a method in the base class as overridable, enabling runtime polymorphism.

intermediate

What happens if you call a non-virtual method through a base class reference?

The base class method is called, even if the derived class has a method with the same name. This is because non-virtual methods are resolved at compile time, not runtime.

beginner

Explain the role of the override keyword in runtime polymorphism.

The <code>override</code> keyword tells the compiler that the derived class method replaces the base class virtual method. This enables the runtime to call the correct method version based on the actual object type.

Which keyword in C# allows a method to be overridden for runtime polymorphism?

A virtual

B static

C sealed

D const

The virtual keyword marks a method as overridable, enabling runtime polymorphism.

What keyword must a derived class method use to override a base class virtual method?

A new

B override

C virtual

D abstract

The override keyword is used in the derived class to replace the base class virtual method.

If a method is not marked virtual, what happens when called through a base class reference?

A Derived class method is called

B Compile error occurs

C Runtime error occurs

D Base class method is called

Non-virtual methods are resolved at compile time, so the base class method is called.

What determines which method is called in runtime polymorphism?

A Runtime type of the object

B Compile-time type of the reference

C Method name length

D Number of parameters

The actual object type at runtime decides which overridden method is executed.

Which of these is NOT required for runtime polymorphism in C#?

A Base class method marked virtual

B Calling method through base class reference

C Method marked as static

D Derived class method marked override

Static methods cannot be overridden and do not support runtime polymorphism.

Describe how runtime polymorphism works in C# with an example.

Think about how a base class pointer can call a method that behaves differently depending on the actual object.

Explain the difference between virtual and non-virtual methods in the context of runtime polymorphism.

Consider what happens when you call a method through a base class reference.