Object Oriented System Development with VB .NET

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Chapter 1

• Object Oriented System Development with VB .NET

2
Introduction

• Object-oriented information system development
  involves analysis, design, and implementation of
  information systems using
• Object-oriented programming languages
• Object-oriented technologies
• Object-oriented techniques
• Object-oriented information system development is
  usually referred to as OO or as the OO
  approach

3
Introduction

• When developing business systems, OO means using
  an
• Object-oriented approach to system analysis (OOA)
• Object-oriented approach to system design (OOD)
• Object-oriented approach to programming (OOP)

4
Understanding OO Development and VB .NET

• The object-oriented approach defines a system as
  a collection of objects that work together to
  accomplish tasks
• The objects can carry out actions when asked
• Each object maintains its own data

5
Understanding OO Development and VB .NET

• The procedural approach defines a system as a set
  of procedures that interact with data
• The data are maintained in files separate from
  the procedures
• When the procedure executes, data files are
  created or updated

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Understanding OO Development and VB .NET
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Object-Oriented Programming

• Object-oriented programming started in the 1960s
• Today many OO programming languages
• Java is a pure OO language
• Microsoft
• C .NET a direct competitor to JAVA
• With VB .NET hopes to dominate OO and Web-based
  development

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The Microsoft .NET Framework and VB .NET

• The .NET framework has two main components
• .NET common language runtime (CLR)
• manages code at execution
• Supports variety of programming languages
• All code compiled to MSIL
• .NET framework class library 
• reusable classes of objects that work with the
  CLR
• Any .NET language can use these classes
• VB .NET is a full-blown OO programming language

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Object-Oriented Analysis and Design

• The standard object-oriented analysis and design
  modeling notation is
• Unified Modeling Language (UML)
• assumes a model-driven approach to analysis and
  design

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Object-Oriented Analysis and Design
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Object-Oriented Analysis and Design

• The system development life cycle (SDLC) is a
  project management framework
• It defines project phases and activities within
  phases
• The phases typically are named
• Planning
• Analysis
• Design
• Implementation
• Support

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Object-Oriented Analysis and Design

• OO developers usually follow an iterative
  approach to analysis, design, and
  implementation 
• Prototyping and joint application development
  (JAD) are usually part of OO development
• Prototyping creating a working model of one or
  more parts of a system to give users a chance to
  see and evaluate something concrete
• During JAD sessions, key system stakeholders and
  decision makers work together to define system
  requirements and designs

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Object-Oriented Analysis and Design

• The following are also required when using OO
  development, as they are in traditional system
  development
• Project management
• Interviewing and data collection
• User interface design
• Testing
• Conversion techniques

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Understanding Object-Oriented Concepts

• Object-oriented development assumes that a system
  is a collection of objects that interact to
  accomplish tasks

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Objects, Attributes, and Methods

• An object (nouns) is a thing that has attributes
  (adjectives) and behaviors (verbs)
• A GUI object
• uses graphics, such as a button or label
• has attributes (adjectives), which are
  characteristics that have values
• have behaviors or methods (verbs), which
  describe what an object can do

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Objects, Attributes, and Methods

• OO systems also contain problem domain objects
• a business system might use
• Customer objects
• Order objects
• Product objects
• What attributes or methods might be assigned?
• Objects interact by sending messages to each
  other
• Tasks to be carried out is the main concept of
  OOA and OOD

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Encapsulation and Information Hiding

• Encapsulation
• an object has attributes and methods combined
  into one unit
• programmer does not need to know the internal
  structure of the object to send messages to it
• Information hiding
• Using encapsulation to hide the internal
  structure of objects, protecting them from
  corruption

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Encapsulation and Information Hiding

• Each object also has a unique identity
• An objects identity must be known for sending a
  message to it
• The objects identity is usually stored as a
  memory address
• Persistent objects are those that are defined as
  available for use over time usually stored in a
  file system

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Classes, Instances, and Associations

• The class defines
• what all objects of the class represent
• Objects can be referred to as instances of the
  class
• When an object is created for the class, it is
  common to say the class is instantiated
• The terms instance and object are often used
  interchangeably

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Classes, Instances, and Associations
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Classes, Instances, and Associations

• Objects maintain association relationships among
  themselves
• Some association relationships are one-to-one,
  and some associations are one-to-many
• UML refers to the number of associations as the
  multiplicity of the association

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Classes, Instances, and Associations
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Inheritance and Polymorphism

• Inheritance
• one class of objects takes on characteristics of
  another class and extends them
• For example
• Person Generalization - Superclass
• Customer
• Employee
• Student
• All are specialization or SubClasses of Person
• Can extend Person with additional Attributes and
  Methods
• What might be another example of Inheritance?

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Polymorphism

• Polymorphism
• the way different objects can respond in their
  own way to the same message
• Classes are polymorphic if their instances can
  respond to the same message differently
• Example
• Bank Account ComputeInterest Method
• Savings
• Certificate of Deposit
• Checking

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Benefits of OO Development

• The two main reasons
• Naturalness
• people usually think about their world in terms
  of objects
• OOA, OOD, and OOP all involve modeling classes of
  objects
• Reuse
• Classes and objects can be invented once and used
  many times
• class libraries that contain predefined classes
• Programmers use these classes to create their own
  objects

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Introducing Three-Tier Design

• The book is organized according to an approach to
  OO development called three-tier design
• Three-tier design requires
• GUI classes Presentation Presentation Tier
• Problem domain classes Business Rules
  Business Tier
• Data access classes Data Data Tier

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Part 1 Object-Orientation and VB .NET
Fundamentals

• Part 1 covers OO concepts and introduces the VB
  .NET programming language
• This part includes chapters 1, 2, 3, 4 and 5

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Part 2 Developing Problem Domain Classes

• Part 2 shows how to use VB .NET to create new
  problem domain classes that are specific to the
  business system being developed
• Part 2 includes chapters 6, 7, 8 and 9

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Part 3 Developing GUI Classes

• Part 3 describes how to create graphical user
  interface classes with which the user can
  interact
• The GUI classes in turn interact with problem
  domain classes
• Part 3 includes chapters 10, 11 and 12

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Chapter 2

• The Visual Studio .NET Development Environment

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Visual Studio .NET

• Visual Studio .NET is
• Integrated Development Environment (IDE) used to
• Create .NET projects
• Compile and execute programs
• Design GUI front ends (forms)
• Debug programming logic
• Contains extensive help facilities
• Dynamic help
• Context-sensitive help F1
• IntelliSense

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Understanding the Start Page
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Creating a Project Using VB .NET

• To create a VB .NET project, identify
• Type of project
• Template to use
• a pattern for creating a specific type of
  application
• Project name and location
• Project Name must be meaningful
• Customize this location

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Understanding the Way VB .NET Organizes Your
Programs

• A project (.vbproj) is a mechanism for grouping
  related files, for example
• Program files (.vb)
• Image files
• Other miscellaneous items
• Startup object must be set
• A solution (.sln) is a container for one or more
  projects
• Solution file appears at the top of the hierarchy
  in Solution Explorer window
• Startup project must be set

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Using the Text Editor

• Visual Studio .NET text editor provides
• Standard text editing capabilities
• Color-coding feature
• VB Specific
• Pretty Print
• Code indentation feature
• Code completion feature

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Setting the Startup Object

• After changing the module name within the source
  code, project properties must be changed to
  identify the new name as the startup object
• Startup object is the module where execution
  begins

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Compiling and Executing a VB .NET Program

• A program can be compiled and executed using
• Options on Build and Debug menus or toolbars
• Shortcut key combinations
• To compile and execute a program using menu
  options
• Click Debug on menu bar
• Click Start Without Debugging

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Using the Visual Form Designer

• A Windows application is one that runs in the
  Windows environment
• When creating Windows applications, a visual form
  editor can be used
• In a visual editor
• Programmer places icons representing various
  components on the screen
• VB .NET generates required programming statements

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Using the Visual Form Designer

• The visual form editor in MDE is Windows Forms
  Designer
• Toolbox contains visual components
• Elements can be selected from Toolbox to
  dynamically design forms
• Properties window is used to adjust properties of
  components on the form

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Creating a Windows Application
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Customizing the Appearance of a Form

• To change title of the form, use Text property in
  Properties window

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Adding Components to a Form

• Toolbox contains components which can be added to
  a form

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Accessing Help

• Most help features can be accessed through
  options on Help menu

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Chapter 3

• VB .NET Programming Fundamentals

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Writing a VB .NET Module Definition

• VB .NET code can be structured as a module
  definition, form definition, or class definition
• Module definition begins with Module and ends
  with End Module
• Form definition is used to create a GUI
• Class definition is written to represent an
  object

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Writing a VB .NET Module Definition

• The VB .NET statements consist of keywords and
  identifiers
• VB .NET identifiers
• Can be of any length
• Can include any letter or number, but no spaces
• Must begin with a letter of the alphabet
• VB .NET code is not case sensitive
• Naming Conventions
• Camel Casing
• Comment lines
• Begin with a single quote (')

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Writing a VB .NET Module Definition

• Procedures
• begin with a procedure header
• identifies the procedure
• describes some of its characteristics
• VB .NET has two types of procedures
• Function
• A Function procedure can return a value
• Sub
• A Sub procedure cannot return a value

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Using VB. NET Variables and Data Types

• A variable named memory location that can
  contain data
• All variables have
• Data type kind of data the variable can contain
  
• Name An identifier the programmer creates to
  refer to the variable
• Value Every variable refers to a memory
  location that contains data. This value can be
  specified by the programmer

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Declaring and Initializing Variables

• When declaring a variable, the programmer must
  specify its data type
• VB .NET has nine primitive data types
• Data types for numeric data without decimals
• Byte, Short, Integer, Long
• Data types for numeric data with decimals
• Single, Double, Decimal
• Other data types
• Boolean, Char

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Declaring and Initializing Variables

• To declare a VB .NET variable, write
• Keyword Dim
• Name to be used for identifier
• Keyword As
• Data type
• Example
• ' declare a variableDim i As Integer

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Declaring and Initializing Variables

• A value can be assigned by the programmer to a
  variable
• Assignment operator () assigns the value on the
  right to the variable named on the left side
• Example
• ' populate the variable
• i 1

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Changing Data Types

• If Option Strict On
• helps prevent unintentional loss of precision
• Casting from one data type to another must be
  done Explicitly
• If Option Explicit On
• the programmer must define a variable before
  using it in a statement
• Required in all programs

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Using Constants

• Constant variable with a value that does not
  change
• Code to declare a constant is identical to the
  code to declare a variable, except
• Keyword Const is used instead of Dim
• Constants must be initialized in the statement
  that declares them
• By convention, constant names are capitalized
  EX. Const SALES_TAX_RATE As Decimal 0.075

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Using Reference Variables

• There are two kinds of variables
• Primitive variable
• Declared with a primitive data type
• Contains the data the programmer puts there
• Reference variable
• Uses a class name as a data type
• Refers to or points to an instance of that class
• Does not contain the data
• Contains the address of an instance of a class
  that contains the data

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Using Reference Variables
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Computing with VB .NET

• VB .NET uses
• Arithmetic operators (, , , /) for addition,
  subtraction, multiplication, and division
• Remainder operator (Mod) produces a remainder
  resulting from the division of two integers
• Integer division operator (\) to produce an
  integer result
• Caret () for exponentiation
• String concatenation operator

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Order of Operations

• Parenthesis
• Exponents
• Multiplication / Division
• Integer Division
• Modulus
• Addition / Subtraction

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Assignment Operators

• , -, , / , \, intTotal intTotal
  intStudentScore
• Can be written
• intTotal intStudentScore

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Computing with VB .NET

• Math class contains methods to accomplish
  exponentiation, rounding, and other tasks
• To invoke a Math class method, write
• Name of the class (Math)
• A period
• Name of the method
• Any required arguments
• Example Math.Pow(5,4)

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Writing Decision-Making Statements

• Selection statements evaluate conditions and
  execute statements based on that evaluation
• VB .NET includes If and Select Case statements
• If statement
• Evaluates an expression
• Executes one or more statements if expression is
  true
• Can execute another statement or group of
  statements if expression is false

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Writing Decision-Making Statements

• Select Case statement
• Evaluates a variable for multiple values
• Executes a statement or group of statements,
  depending on contents of the variable being
  evaluated

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Writing If Statements
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Writing If Statements

• VB .NET If statement has two forms Simple If and
  If-Else
• Simple If
• Evaluates an expression
• Executes one or more statements if expression is
  true
• If expressions then statement(s)End If

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Writing If Statements

• If-Else
• If expression Then statements
• Else
• statements
• End If

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Logical Operators

• AND
• OR
• NOT
• If (intAge gt 20) And (intAge lt 35) then
• statements
• End if
• .NET will short circuit conditional testing as
  soon as it can determine result

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Nested IFs
If intAge gt 20 Then If intAge lt 35
Then statements
Else statements End If Else
statementsEnd If
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Writing Select Case Statements

• Select Case statement
• Acts like a multiple-way If statement
• Transfers control to one of several statements,
  depending on the value of an expression
• Select intStudentAgeCase is gt 21
  statements
• Case 17 to 18
• statements
• Case 10,12,14
• statementsCase Else
• statements
• End Select

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Writing Loops

• Loops repeated execution of one or more
  statements until a terminating condition occurs
• Three types of loops
• Do While (condition is true) While (condition
  is true)
• statements
  statements
• Loop
  End While
• Do Until (until condition is true)
• statements
• Loop
• For Next
• Early out
• Exit Do, Exit For, Exit While

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Writing Post-Test Loops

• Programming languages provide two kinds of loops
• Pre-test loop tests the terminating condition at
  the beginning of the loop
• Post-test loop tests the terminating condition at
  the end of the loop

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Writing Post-Test Loops

• Do
• statements
• Loop While (condition is true)
• Do
• statements
• Loop Until (condition becomes true)
• For Next and While loops are always pre-test

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Writing For Next Loops

• VB .NET For Next loop
• loop counter
• initialization
• incrementing defaults to 1, can be any /-
  value
• pre-test logic Example
• ' for next loop
• For i 1 To 3 Step 1
• Console.WriteLine("for next loop i " i)
• Next

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Writing Nested Loops

• Nested loop
• A loop within a loop
• Can be constructed using any combination of Do
  While, Do Until, or For Next loops

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Declaring and Accessing Arrays

• Arrays create a group of variables with the same
  data type
• In an array
• Each element behaves like a variable
• All elements must have the same data type
• Elements either can contain primitive data or can
  be reference variables

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Declaring and Accessing Arrays

• Arrays can be either one-dimensional or
  multi-dimensional
• One-dimensional array consists of elements
  arranged in a row
• Two-dimensional array has both rows and columns
• Three-dimensional array has rows, columns, and
  pages
• VB .NET implements multi-dimensional arrays as
  arrays of arrays

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Using One-Dimensional Arrays

• Declare a 5-element array with of integers
• ' declare an integer array with 5 elements
• Dim intTestScores(4) As Integer
• Accessing individual array elements intTestScores
  (0)
• Subscript (Index) must be an integer
• Literal - (1)
• Identifier (intCounter)
• Relative reference (intCounter 2)
• Expression (intAge intMultiplier)
• Length attribute returns number of elements

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Using One-Dimensional Arrays

• Code to initialize the array elements 
• testScores(0) 75
• testScores(1) 80testScores(2)
  70testScores(3) 85testScores(4) 90
• An array can be declared and populated using a
  single statement
• Dim testScores() As Integer 75, 80, 70, 85,
  90

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Using One-Dimensional Arrays
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Using Multidimensional Arrays

• Conceptually
• A two-dimensional array is like a table with rows
  and columns
• A three-dimensional array is like a cube, with
  rows, columns, and pages
• Each dimension has its own index
• Declare an Integer array with five rows and two
  columns
• Dim testScoreTable(4, 1) As Integer
• Length attribute returns total number of
  elements Example testScoreTable.Length returns
  10
• GetLength(dimension) returns the number of
  elements in a specific dimensionExample
  testScoreTable.GetLength(0) returns 5

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Using Multidimensional Arrays
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