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Data Structures and Algorithms
with Object-Oriented Design Patterns in C# |
Every member of a class, be it a field or a method,
has an access control attribute
which affects the manner in which that member can be accessed.
The members of a class can be private, public,
protected, internal, or protected internal.
For example,
the fields real and imag
declared in Program 
are both private.
Private members can be used only by methods
of the class in which the member is declared.
On the other hand,
public members of a class can be used by any method in any class.
All of the operations defined in Programs , and
all declared to be public.
In effect, the public part of a class defines the interface to that class and the private part of the class encapsulates the implementation of that class. By making the implementation of a class private, we ensure that the code which uses the class depends only on the interface and not on the implementation of the class. Furthermore, we can modify the implementation of the class without affecting the code of the user of that class.
Protected members are similar to private members.
That is, they can be used by methods
of the class in which the member is declared.
In addition, protected members can also be
used by methods of all the classes derived
from the class in which the member is declared.
The protected category is discussed again in Section .
An internal member can be accessed by any method in the same program in which the member is declared. Finally, a protected internal member can be accessed by methods in the class in which the member is declared, by methods in classes dervied from the class in which the member is declared, and any method in the same program in which the member is declared.
Copyright © 2001 by Bruno R. Preiss, P.Eng. All rights reserved.