C# 5.0 Programmer's Reference

246 ❘ CHAPTER 11 OOP Concepts
The three main sets of characteristics of a class are the properties, methods, and events that it
defines. The public (externally visible) properties, methods, and events let the program work with
the class:
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A property is some sort of data value. It may be a simple value (such as a string or int), or
it may be a more complex item (such as an array, list, or object containing its own properties,
methods, and events). Properties determine some feature of an object such as its name, color,
or behavior.
A method is a routine that performs some action. A method makes an object defined by the
class do something.
An event provides notification that something happened to an object defined by the class. An
event can invoke other pieces of code to tell other parts of the program that something has
happened to the object.
For a concrete example, imagine a Job class that represents a piece of work to be done by an
employee. This class might have the properties shown in the following table.
Property
JobDescription
EstimatedHours
ActualHours
Status
ActionTaken
Customer
AssignedEmployee
Purpose
A string describing the job.
The number of hours initially estimated for the job.
The actual number of hours spent on the job.
An enumeration giving the job’s status (New, Assigned,
InProgress, or Complete).
A string describing the work performed, parts installed, and
so forth.
An object of the Customer class that describes the customer for
whom the job is performed. (That class has properties such as
Name, Address, PhoneNumber, and ContractNumber.)
An object of the Employee class that describes the employee
assigned to the job. (That class has properties such as Name,
PhoneNumber, EmployeeId, and SocialSecurityNumber.)
The JobDescription, EstimatedHours, ActualHours, Status, and ActionTaken properties are
relatively simple string and numeric values. The Customer and AssignedEmployee properties
are objects themselves with their own properties, methods, and events.
This Job class might provide the methods shown in the following table.
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