Programming C#

The Root of all Classes: Object

All C# classes, of any type, are treated as if they ultimately derive from System.Object. Interestingly, this includes value types!

A base class is the immediate “parent” of a derived class. A derived class can be the base to further derived classes, creating an inheritance “tree” or hierarchy. A root class is the topmost class in an inheritance hierarchy. In C#, the root class is Object. The nomenclature is a bit confusing until you imagine an upside-down tree, with the root on top and the derived classes below. Thus, the base class is considered to be “above” the derived class.

Object provides a number of methods that subclasses can and do override. These include Equals( ) to determine if two objects are the same, GetType( ), which returns the type of the object (discussed in Chapter 18), and ToString( ), which returns a string to represent the current object (discussed in Chapter 10). Table 5-1 summarizes the methods of Object.

Table 5-1. The methods of Object

Method	What It Does
Equals( )	Evaluates whether two objects are equivalent.
GetHashCode( )	Allows objects to provide their own hash function for use in collections (see Chapter 9).
GetType( )	Provides access to the type object (see Chapter 18).
ToString( )	Provides a string representation of the object.
Finalize( )	Cleans up nonmemory resources (see Chapter 4).
MemberwiseClone( )	Creates copies of the object; should never be implemented by your type.