Object oriented techniques

Object-Oriented
Techniques

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Objectives


Objectives
• Understand how derived classes inherit from
base classes


Objectives
base classes
• Explore how to add and modify members in
derived classes


Objectives
base classes
derived classes
• Learn to control how derived classes inherit
from base classes


Objectives
base classes
derived classes
from base classes
• Understand how to create and use interfaces


Objectives
base classes
derived classes
from base classes
• Understand how to create and use interfaces
• Explore techniques for organizing your classes


Agenda


Agenda
• Inheritance


Agenda
• Inheritance
• Interfaces


Agenda
• Inheritance
• Interfaces
• Organizing Classes


Inheritance


Inheritance
• Inefficient to have similar classes with the same
members


Inheritance
members
• Create a more generic (base) class and then
inherit (derive) from the generic class


Inheritance
members
• Derived classes inherit the members of the base
class


Inheritance
members
class
• Inheritance defines an “is-a” relationship


Inheritance
members
class
 A corporation is a customer


Inheritance
members
class
 A corporation is a customer
 An individual is a customer


Inheritance Hierarchy


• Customer is the base class and is the most
generic representation of a customer


• Customer is the base class and is the most
generic representation of a customer
• Corporation and Individual are derived classes,
inheriting from the base class


The “is-a” Relationship


• Be thorough when defining the “is-a” relationships
among objects in your code


• Be thorough when defining the “is-a” relationships
among objects in your code
• If differences between two types of customers (like
Corporation and Individual) are significant, it may
warrant making separate classes such as Domestic and
Foreign


Adding Members to Derived Classes


• Common properties and methods can go in the
base class


• Common properties and methods can go in the
base class
• Unique properties and methods can be added to
derived classes


Overriding Derived Members


• Override a property or method in a derived class
to change its behavior


• Override a property or method in a derived class
to change its behavior
• You are replacing the base class member with
the derived class member


Overloading Derived Members


• Overload a property or method of a base class
to create a specialized version in a derived class


• Overload a property or method of a base class
to create a specialized version in a derived class
• The base class member still exists and can be
used in addition to a derived class member


Calling Base Class Members


Calling Base Class Members
• Members of a derived class can call members of
the base class


Abstract Classes and Members


• An abstract class is designed to be generic and
is incomplete


is incomplete
• You cannot create an instance of it and can only
derive from it


is incomplete
derive from it
• Abstract class can contain abstract properties
and members


is incomplete
derive from it
and members
 Derived classes cannot call these properties from the
abstract class


is incomplete
derive from it
and members
 Derived classes cannot call these properties from the
abstract class
 They must implement them on their own


Sealed Classes and Members


• Seal a class to prevent inheriting from it


• Seal a class to prevent inheriting from it
• Seal a member in a derived class to prevent
further derived classes from overriding it


Interfaces


Interfaces
• Define a set of properties and methods that a
class will implement


Interfaces
• Contain no implementation code


Interfaces
• A class must implement all members defined in
an interface


Interfaces
an interface
 Visual Studio adds member declarations
automatically, you add code to implement members


Interfaces
an interface
 You can override and overload interface members


Implementing an Interface


an interface


an interface
• Class can implement multiple interfaces but can
only derive from one class


an interface
• Class can implement multiple interfaces but can
only derive from one class
• Use interfaces to implement smaller sets of
members and to enable classes to implement
only interfaces they need

Interfaces in the .NET Framework


• The .NET Framework contains many interfaces
you can use


you can use
• IComparable provides a general way of
comparing value types or classes


you can use
 Call CompareTo as a method of one type


you can use
 Call CompareTo as a method of one type
 Pass as argument the type you are comparing the
first type with


Organizing Classes


Organizing Classes
• Classes are a good way to organize your code


Organizing Classes
• Classes are a good way to organize your code
• You can also organize your classes


Partial Classes


Partial Classes
• Helpful on teams where you are writing some
class methods and other developers are writing
the rest


Partial Classes
the rest
• Split the class definition across multiple files


Partial Classes
the rest
• Compiler combines the partial classes into one
class


Partial Classes
the rest
• Compiler combines the partial classes into one
class
• Calling class uses class the same whether it is
made up of partial classes or not


Nested Classes


Nested Classes
• Class defined within another class


Nested Classes
• Organize class members so they are easier to
use at runtime


Nested Classes
use at runtime
• Group members of Customer class


Nested Classes
use at runtime
 Customer.Information


Nested Classes
use at runtime
o CustomerName, City, Region, etc


Nested Classes
use at runtime
 Customer.Financial


Nested Classes
use at runtime
o CreditLimit, ChangeCreditLimit


Nested Classes
use at runtime
 Customer.Sales


Nested Classes
use at runtime
 Customer.Sales
o RecordSales


Namespaces


Namespaces
• A way to organize related classes into groups


Namespaces
 System.Data contains classes to work with data
once you have retrieved it from a data source


Namespaces
• Namespaces can be nested


Namespaces
 System.Data.SqlClient contains classes to retrieve
data from SQL Server


Namespaces
 System.Data.SqlClient contains classes to retrieve
data from SQL Server
 System.Data.OracleClient contains classes to
retrieve data from Oracle


Namespaces
• By default, the application namespace is the
name of the project


Namespaces
name of the project
• You can change this in Project Designer


Namespaces
name of the project
• You can change this in Project Designer
• Create your own namespaces to organize
classes in class libraries


Learn More!


Learn More!
• This is an excerpt from a larger course. Visit
www.learnnowonline.com for the full details!


Learn More!

• Learn more on SlideShare


Learn More!

• Learn more on SlideShare
 Object-Oriented JavaScript


Object oriented techniques

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