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Listing 9 . Cannot be assigned to C.

//Following will not execute. // Causes a runtime exception.//C v2 = (C)var;

The code in Listing 9 attempts to cast the reference to type C and assign it to a reference variable of type C .

A runtime exception

Although the program will compile, it won't execute. An attempt to execute the statement in Listing 9 results in an exception at runtime.

As a result, it was necessary to convert the statement into a comment in order to execute the program.

Another failed attempt

Similarly, an attempt to cast the reference to type B and assign it to a reference variable of type C , as shown in Listing 10 , won't compile.

Listing 10 . Another failed attempt.

//Following will not compile //C v3 = (B)var;//Pause until user presses any key. Console.ReadKey();}//end Main }//end class Polymorph02

The problem here is that the class C is not a superclass of the class named B . Therefore, a reference of type B is not assignment-compatible with a reference variable of type C .

Again, it was necessary to convert the statement to a comment in order to compile the program.

The end of the program

Listing 10 signals the end of the Main method, the end of the class, and the end of the program.

Run the program

I encourage you to copy the code from Listing 11 . 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.

Run my program

Click here to download a zip file containing my version of the program. Extract the folder named Polymoeph02 from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to the project folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as described in the earlier module titled Getting Started .

Summary

This module discusses type conversion for primitive and reference types.

A value of a particular type may be assignment-compatible with variables of other types.

If the type of a value is not assignment-compatible with a variable of a given type, it may be possible to perform a cast on the value to change its typeand assign it to the variable as the new type. For primitive types, this will often result in the loss of information.

In general, numeric values of primitive types can be assigned to any variable whose type represents a numeric range that is as wide as or wider than the rangeof the value's type. (Values of type bool can only be assigned to variables of type bool .)

With respect to reference types, the reference to an object instantiated from a given class can be assigned to any of the following without the use of a cast:

  • Any reference variable whose type is the same as the class from which the object was instantiated.
  • Any reference variable whose type is a superclass of the class from which the object was instantiated.
  • Any reference variable whose type is an interface that is implemented by the class from which the object was instantiated.
  • Any reference variable whose type is an interface that is implemented by a superclass of the class from which the object was instantiated.
  • A couple of other cases involving interfaces that extend other interfaces.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
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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