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In some cases, multiple methods have the same name, but different formal argument lists. This is polymorphism implemented using overloaded methods. I explained this form of polymorphism in an earlier module.

In other cases, multiple methods have the same name, same return type, and same formal argument list. This is method overriding , which is the main topic of this module.

The essence of runtime polymorphic behavior

Methods are called on references to objects. Typically, those references are stored in reference variables, or in the elements of a collection such as anarray, stack, or queue.

The decision process

With runtime polymorphism based on method overriding , the decision regarding which version of a method will be executed is based on the actual type of the object whose reference is stored in the reference variable, and not on the type of the reference variable on which the method is called.

Stated differently, the type of the reference determines which methods can be called . The type of the object determines which method (from that set of allowable methods) will be called .

Late binding

The decision regarding which version of the method to call cannot be made at compile time. That decision must be deferred and made at runtime. This issometimes referred to as late binding .

Operational description of runtime polymorphism

Here is an operational description of runtime polymorphism as implemented in C# through inheritance and method overriding:

  • Assume that a class named SuperClass defines a method named method .
  • Assume that a class named SubClass extends SuperClass and overrides the method named method .
  • Assume that a reference to an object of the class named SubClass is assigned to a reference variable named ref of type SuperClass .
  • Assume that the method named method is then called on the reference variable using the following syntax: ref.method() .
  • Result: The version of the method named method that will actually be executed is the overridden version in the class named SubClass . The version that is defined in the class named SuperClass will not be not executed.

This is runtime polymorphism.

Runtime polymorphism is very powerful

As you gain more experience with C#, you will learn that much of the power of OOP using C# is centered on runtime polymorphism using class inheritance,interfaces, and method overriding. (The use of interfaces for polymorphism will be discussed in a subsequent module.)

An important attribute of runtime polymorphism

This is worth repeating:

The decision regarding which version of the method to execute is based on the actual type of object whose reference isstored in the reference variable, and not on the type of the reference variable on which the method is called.

Why is it called runtime polymorphism?

The reason that this type of polymorphism is often referred to as runtime polymorphism is because the decision regarding which version of the method to execute cannot be made until runtime. The decision cannot be made at compiletime (as is the case with overloaded methods).

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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