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However, while necessary, that is not sufficient to ensure runtime polymorphic behavior.

Must define or inherit the method

The type of the reference variable must also be the name of a class that either defines or inherits a version of the method that will ultimately becalled on the object.

Since the class named Object does not define (or inherit) the method named m , a reference of type Object does not qualify as a participant in runtime polymorphic behavior in this case. The attempt to use it as a participant results in the compiler error given above.

One additional scenario

Before leaving this topic, let's look at one additional scenario to help you distinguish what is, and what is not, runtime polymorphism. Consider the codeshown in Listing 6 .

Listing 6 . Not polymorphic behavior.

//Instantiate obj of class A var = new A();//Call the method on it ((A)var).m();// Pause until the user presses any key. Console.ReadKey();}//end Main }//end class Polymorph03

A new object of type A

The code in Listing 6 instantiates a new object of the class named A , and stores the object's reference in the original reference variable named var of type Object .

As a side note, this overwrites the previous contents of the reference variable with a new reference and causes the object whose reference waspreviously stored there to become eligible for garbage collection.

Downcast and call the method

Then the code in Listing 6 casts the reference down to type A , (the type of the object to which the reference refers) , and calls the method named m on the downcast reference.

The output

As you would probably predict, this produces the following output on the computer screen:

m in class A

In this case, the version of the method defined in the class named A , (not the version defined in B) was executed.

Not polymorphic behavior

Once again, in my view, this is not runtime polymorphic behavior (at least it isn't a very useful form of polymorphic behavior) . This code simply converts the type of the reference from type Object to the type of the class from which the object was instantiated, and calls one ofits methods. Nothing special takes place regarding a selection among different versions of the method.

Once again, what is runtime polymorphism?

As I have discussed in this module, runtime polymorphic behavior based on inheritance occurs when

  • The type of the reference is a superclass of the class from which the object was instantiated.
  • The version of the method that is executed is the version that is either defined in, or inherited into, the class from which the object wasinstantiated.

And that is probably more than you ever wanted to hear about runtime polymorphism based on inheritance.

A future module will discuss runtime polymorphism based on the C# interface. From a practical viewpoint, you will find the rules to be similar but somewhatdifferent in the case of the C# interface.

Run the program

I encourage you to copy the code from Listing 7 . Use that code to create a C# console project. Compile and run the project. Experiment with the code,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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