C# 0 The Complete Reference

Main( )

 that 

shapes

 is declared as an array of 

TwoDShape

 objects. However, the elements of this array 

are assigned 

Triangle

,

Rectangle

, and 

TwoDShape

 references. This is valid because a base 

class reference can refer to a derived class object. The program then cycles through the array, 

displaying information about each object. Although quite simple, this illustrates the power 

of both inheritance and method overriding. The type of object stored in a base class reference 

variable is determined at runtime and acted on accordingly. If an object is derived from 

TwoDShape

, then its area can be obtained by calling 

Area( )

. The interface to this operation 

is the same no matter what type of shape is being used.