C# 0 The Complete Reference

Width

 and 

Height

 inside the 

Area( )

 method is illegal. Since 

Width

 and 

Height

 are now private, they are accessible only 

to other members of their own class. Derived classes have no access to them.

R

EMEMBER

R

EMEMBER

A private class member will remain private to its class. It is not accessible to any code 

outside its class, including derived classes.

At first, you might think that it is a serious restriction that derived classes do not have 

access to the private members of base classes because it would prevent the use of private 

members in many situations. However, this is not true; C# provides various solutions. One 

is to use 

protected

 members, which is described in the next section. A second is to use public 

properties to provide access to private data.

As explained in the previous chapter, a property allows you to manage access to an 

instance variable. For example, you can enforce constraints on its values, or you can make 

the variable read-only. By making a property public, but declaring its underlying variable 

private, a derived class can still use the property, but it cannot directly access the underlying 

private variable.

Here is a rewrite of the