C# Programming: Object-Oriented Features and Component-Based Development, Slides of Advanced Computer Programming

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C# Programming: From Problem Analysis to Program Design 1

Advanced

Object-Oriented

Programming

Features

C# Programming: From Problem Analysis to Program Design 3rd Edition

C# Programming: From Problem Analysis to Program Design 2

Chapter Objectives

• Learn the major features of object-oriented languages
• Design and develop multitier applications using component-based development methods
• Use inheritance to extend the functionality of user- defined classes
• Create abstract classes that include abstract methods

C# Programming: From Problem Analysis to Program Design 4

Chapter Objectives ( continued )

• Investigate static versus dynamic typing and become aware of when dynamic and var types are used
• Work through a programming example that illustrates the chapter’s concepts

C# Programming: From Problem Analysis to Program Design 5

Object-Oriented Language

Features

• Abstraction
  • Abstract or identify the objects involved in the problem
• Encapsulation
  • Packaging data and behaviors into a single unit
• Inheritance
  • Reuse of code through extending program units
• Polymorphism
  • Multiple implementations of the same behaviors

C# Programming: From Problem Analysis to Program Design 7

Component-Based Development

( continued )

• Multitier applications
  • Data access tier for accessing data from text files and databases
  • Graphical user interface tier for user interaction
    • Windows
    • Web
• Components implemented through classes in C#
• Class library files with a dynamic link library (DLL) extension

C# Programming: From Problem Analysis to Program Design 8

Inheritance

• Enables you to:
  • Create a general class and then define specialized classes that have access to the members of the general class
• Associated with an "is a" relationship
  • Specialized class “is a” form of the general class
• Classes can also have a "has a" relationship, not associated with inheritance - "has a" relationship is associated with containment or aggregation

C# Programming: From Problem Analysis to Program Design 10

Inheriting from Other .NET FCL

Classes

• Add functionality to programs with minimal programming
• Extend System.Windows.Forms.Form class to build GUIs (Button, Label, TextBox, ListBox) Base class

Derived class

Figure 11-3 Derived class

C# Programming: From Problem Analysis to Program Design 11

Creating Base Classes for

Inheritance

• Can define your own classes from which other classes can inherit
• Base class is called the super or parent class
• Data members are defined with a private access modifier
• Constructors are defined with public access modifiers
• Properties offer public access to data fields

C# Programming: From Problem Analysis to Program Design 13

Overriding Methods ( continued )

• Example of polymorphism
  • ToString( ) method can have many different definitions
  • ToString( ) uses the virtual modifier, implying that any class can override it
• Derived classes inherit from a base class
  • Also called subclasses or child classes
• Protected access modifiers
  • Access only to classes that derived from them
  • Access to change data in the base class

C# Programming: From Problem Analysis to Program Design 14

Calling the Base Constructor

• To call the constructor for the base class, add keyword :base between the constructor heading for the subclass and the opening curly brace public Student(string id, string fname, string lname, string maj, int sId) :base (id, lname, fname) // base constructor arguments {...
• Base constructor must have a constructor with matching signature

C# Programming: From Problem Analysis to Program Design 16

Relationship

between the Person and Student Classes

Figure 11-5 Inheritance class diagram

C# Programming: From Problem Analysis to Program Design 17

Making Stand-Alone

Components

• Compile class and create an assembly
  • Assemblies are units configured and deployed in .NET
• Classes can be compiled and stored as a dynamic link library (DLL) instead of into the EXE file type
• Adds a reference to the DLL
  • That referenced file with the .dll extension becomes part of the application’s private assembly

C# Programming: From Problem Analysis to Program Design 19

Build Instead of Run to Create DLL

• Create the parent class first in order to use IntelliSense
• Create the subclass class in the same way as usual, except Build instead of Run the project to create the DLL

Figure 11-7 Attempting to run a class library file

C# Programming: From Problem Analysis to Program Design 20

Add Reference to Base Class

Figure 11-8 Adding a reference to a DLL

One of the first things to do is Add a Reference to the Parent DLL