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The override declaration

Note the use of the override declaration in Listing 2 . In C#, if one method overrides another, it is necessary to declare that fact.

Once again, if you come from a Java background, you will note that this is just the reverse of the situation in Java. In Java, a method whose name,return type, and formal argument list matches an inherited method will automatically override the inherited method.

A compiler warning

If you fail to make the override declaration in Listing 2 , you will get a compiler warning that reads something like the following:

warning CS0114: 'B.m()' hides inherited member 'A.m()'. To make the current member override that implementation,add the override keyword. Otherwise add the new keyword.

Overriding versus hiding

I'm not going to get into a discussion of the difference between overriding and hiding in this module. Perhaps I will find the time to provide such adiscussion in a future module.

Behavior of the overridden method

Like the inherited version of the method, the overridden version displays a message indicating that it has been called. However, the message is differentfrom the message displayed by the inherited version discussed above. The overridden version tells us that it is defined in the class named B .

According to the current jargon, the behavior of the overridden version of the method is appropriate for an object instantiated from the classnamed B .

Again, this message will allow us to determine which version of the method is executed in each case discussed later.

The driver class

Listing 3 shows the beginning of the driver class named Polymorph03 .

Listing 3 . Beginning of the driver class.

public class Polymorph03 { public static void Main() {Object var = new B(); //Following will compile and run((B)var).m();

A new object of the class B

The code in the Main method begins by instantiating a new object of the class named B , and assigning the object's reference to a reference variable of type Object .

This is legal because an object's reference can be assigned to any reference variable whose type is a superclass of the class from which the objectwas instantiated. The class named Object is the superclass of all classes.

Downcast and call the method

If you have read the module titled Xna0112-Type Conversion, Casting, and Assignment Compatibility , it will come as no surprise to you that the second statement in the Main method, which casts the reference down to type B and calls the method named m on it, will compile and execute successfully.

Which version was executed?

The execution of the method produces the following output on the computer screen:

m in class B

By examining the output, you can confirm that the version of the method that was overridden in the class named B is the version that was executed.

Why was this version executed?

This should also come as no surprise to you. The cast converts the type of the reference from type Object to type B .

You can always call a public method belonging to an object using a referenceto the object whose type is the same as the class from which the object was instantiated.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
I rally confuse this number And equations too I need exactly help
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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