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The overloaded version of the method named m , defined in the class named A , is inherited into the class named B . Hence, it can be called on a reference to an object instantiated from the classnamed B .
The other two versions of the method named m are defined in the class named B . Thus, they also can be called on a reference to an object instantiated from the class named B .
As you would expect from the code that you examined for each of the three methods, the output produced by sending messages to the object asking it toexecute each of the three overloaded versions of the methods named m is shown in Figure 1 .
Figure 1 . Screen output from the project named Polymorph01.
m()
m(int x)m(String y) The values of the parameters passed to the methods do not appear in the output. In this program, the parameters are used solely to make it possible forthe compiler to select the correct version of the overloaded method to execute in each case.
This output confirms that each overloaded version of the method was properly selected for execution based on the matching of method parameters to the formalargument list of each method.
I encourage you to copy the code from Listing 4 . Use that code to create a C# console project. Compile and run the project. Experiment with thecode, making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.
Click here to download a zip file containing my version of the program. Extract the folder named Polymorph01 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 .
Overloaded methods have the same name and different formal argument lists. They may or may not have the same return type.
The word polymorphism means something like one name, many forms . Polymorphism manifests itself in C# in the form of multiple methods having thesame name.
Polymorphism manifests itself in three distinct forms in C#:
This module concentrates on method overloading, sometimes referred to as compile-time polymorphism .
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freelyavailable on cnx.org and that it was made and published without my prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
A complete listing of the C# program discussed in this module is provided in Listing 4 .
Listing 4 . Project Polymorph01.
/*Project Polymorph01
Copyright 2009, R.G.BaldwinThis program illustrates method
overloading, both within a class, andup the inheritance hierarchy.
Program output is:m()m(int x)
m(String y)**************************************/
using System;class A : Object {
public void m() {Console.WriteLine("m()");
}//end method m()}//end class A
//===================================//class B : A {
public void m(int x) {Console.WriteLine("m(int x)");
}//end method m(int x)//---------------------------------//
public void m(String y) {Console.WriteLine("m(String y)");
}//end method m(String y)}//end class B
//===================================//public class Polymorph01 {
public static void Main() {B var = new B();
var.m();var.m(3);
var.m("String");//Pause until the user presses
// a key.Console.ReadKey();
}//end Main}//end class Polymorph01 -end-
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