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08.18.05
Virtual Methods & Polymorphism
In C#
 By Pawan
Bangar
Virtual methods allow object oriented languages to express polymorphism.This means
that a derived class can write a method with the same signature as a method in
its base class, and the bas class will call the derived class's method.By default
in java, all methods are virtual.
In C# like c++, the virtual keyword is needed to specify that a method should
override a method (or implementaion an abstract method) of its base class.
Class
B {
public virtual void foo () {}
}
ClassD : B {
public override void foo () {}
}
Attemting to override a non-virtual method will results in a compile-time error
unless the "new" keyword is added to the declaration, indicating the method is
intentionally hiding the base clas's method.
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Class
N : D {
public new void foo () {}
}
N n = new N ();n.foo; // calls N's foo ((D)n).foo; // calls D's foo
((B)n).foo(); //calls D's foo
In contrast to both c++ and Java, requiring the override keyword makes it more
clear as to what methods are overridden when looking at source code.However, requiring
the use of the virtual methods has its pros and cons. The first pro is the slightly
increased execution speed from avoiding virtual methods.The second pro is to make
clear what methods are intended to be overridden.However, this pro can also be
a con.Compare the default option of leaving out a final modifier in Java Vs leaving
out a virtual modifier in C++. The default option in Java may make your program
slightly less efficient, but in C++ it may prevent extendibility, albeit unforeseen,
by the implementer of the base class.
About the Author:
Presently working in the capacity of the Technical Director of Birbals, an e-consulting
firm based in India dedicated in providing innovative and effective web, Hospitality
and consultancy services to public, private and non-profit organizations. Successfully
founded Birbals and other IT companies like Ebirbals and SeoBirbals. |
