Object Oriented Programming I

VB.NET

ITCS 212
Object Oriented Programming I
By: Mrs. Marie Tupaz

What is Program, Programming and Basic Procedures

INTRO TO PROGRAMMING

What is Programming?

• Program
• a set of directions for the computer to
complete a task

• a sequence of instructions written to
perform a specified task with a computer


Programming
• process of designing,
writing, testing, debugging, and
maintaining the source
code of computer programs
• Wikipedia

• giving the computer directions for
completing a task

A computer is essentially a trained
squirrel: acting on reflex,
thoughtlessly running
Back and forth and storing away nuts
until some other stimulus makes it
do something else.
Ted Nelson

What is Programming

• Example :

• Baking a Cake
• Making an Leche Plan


• Basic Task
Input

Process

Output


• Input – Key in data in computer
• Process – the task given or work of the
program
• Output – the results

Every Data must be declared before you
can use and its called Declaration

What is programming?

Baking a Cake:

• Declarations : the measuring cups, the measuring
spoons, the mixing bowl, and the cake pan. You must
make sure you have these before you start.

• Input : the ingredients, the cake mix, the eggs, the water,
and such.

• processing: the mixing and the baking – all the steps
needed to turn your ingredients into a cake.

• Output : the cake.

Basic Programming Procedure

3 Category
• Sequence - order of commands in a program
(Washing dishes)
• Selection - enable the computer to make
decisions : Depending on decision, a different set of
directions must be followed (laundry)
• Repetition - allow the computer to repeat the
same series of steps (Brushing teeth)


• Program Errors
provide computer with precise directions for
the task and provide these directions in a
language the computer will understand

If directions are wrong then the computer
makes “mistakes.”

How to minimize this mistakes?


• Algorithm
• What is Algorithm?
• is a step-by-step procedure

• Lit. the description of the steps to solve the
problem


Interface/Instruction
=
Human/ Computer connection


Developer/User
• Developer - is the person that develops
the specifications, designs the program,
creates the algorithm, writes the code,
and tests the program
• User: is the person that uses the
finished program.
• User part in program
designing the program, and testing it


Design Time/Runtime

• Design Time - when the program is
developed, the interface is created, and
the code is written
• Run Time - program is running

Remember
At design time a developer
decides everything that a program
will be and can do.
At runtime, the program executes
the commands given to it at design
time.


Form/Code

• Form window - often called the
interface and is what the user sees
when the program runs
• Code window – where the directions
the program is written and must never
sees by the user


• Objects/Events

• Objects – controls
• Events – the ways a user interacts with
the computer


Code Files/Program

• To create or modify a program, you
need the project folder and its files.
These are used to create the
executable file or .exe -- Finished
program found in bin folder

• .exe –, standalone program that can run
even without VS

Visual Basic.NET
• Easier to Use
• Streamlined and Modernized
• More Powerful than VB 6.0
• Higher level of access to system
resources that in the past required
the use of languages like C++
• True Object Inheritance
• Garbage Collection for better
memory management

Visual Studio .NET 2003

• Released April 27, 2003
• J#
• Mobile Web Applications: using the
integrated ASP.NET Web Forms and
the Visual Studio .NET Web Forms
Designer, Visual Basic and C#
developers can easily build thin-
client Web-based applications that
render intelligently on more than 200
devices, including wireless
application protocol (WAP) phones,
wireless personal digital assistants
(PDAs), and pagers.

New Web Development
• Programming for the Web vs.
Windows
• New set of controls
• Web page layout
• ASP.NET
• ADO.NET
• Mobile Applications
• Convert Projects

Just an Upgrade???
• NO!
• VB.NET omits quite a few forms of
syntax
• VB.NET requires a total rewrite rather
than a simple port of code
• VB.NET is not dependent on older
libraries such as VBA runtime and
ADO (ActiveX Database Object)

Forms are now Classes

• In VB6, forms were
classes, but you
rarely treated them
that way
• VB .NET shows the
code that instantiates
the form
• To show additional
forms, you must first
instantiate them

Form Changes

• Forms have undergone a number
of changes. These include:
• The Forms engine is now
WinForms and add such features
as docking and opacity
• Forms are classes
• A Component Tray holds non-
visual controls at design-time

VB.NET or C#.NET
• C# is a new language that
was designed to be
friendly to programmers
who are already
proficient in C or C++
• Either language can be
used to write software
that takes full advantage
of the CLR and .NET
framework

New Tools

• Calendar Tool
• Date Picker Calendar
• Opacity Control
• Timer does not lay on form
• Command Buttons are now called
Buttons
• Use ―btn‖ for prefix

More Changes

• The Editor window (formerly the
Code window)
• Lots more IntelliSense help;
can be confusing
• Declarations section replaces
General Declarations
• Collapsible Regions in code
(Plus signs)

Collapsed Regions
Tabs
Method List

Class
List

Collapsed
Region

Collapsed
Procedure

General Changes
• There have been a number of changes in
VB .NET. General changes include:
• Form changes
• Option Strict
• Event Handler changes
• Default Properties
• Calling Subs and Functions
• Boolean operators
• Using CTRL + Space to finish variables

The Component Tray

• In VB6, controls that were only
visible at design-time still appeared
on the form in the IDE
• Such as the Timer control
• VS .NET places controls that are
invisible at runtime in a small area
below the form
• This area is the Component Tray

Forms are now Classes

• In VB6, forms were classes, but you
rarely treated them that way
• VB .NET shows the code that
instantiates the form
• To show additional forms, you must
first instantiate them

Calls to Subs and Functions
Require Parentheses
• In VB6, you called a Sub without
parentheses
AddOrder OrderNum, OrderDate
• You could use the Call statement, which
required parenthese
Call AddOrder(OrderNum, OrderDate)
• .NET always requires parentheses for a
Sub, as well as with Functions

New Boolean Operators

• The And and Or keywords do not short-
circuit in VB and VB .NET
• Both sides of an operator are evaluated, even
if the first option invalidates the statement
• VB .NET adds two short-circuiting
Boolean operators:
• AndAlso
• OrElse

Boolean Operators Example

Dim x As Integer
x = 0
If x>2 And 5x > 1 Then ...
• This If statement is already false on
the x>2 part, but 5x is still checked
because And does not short-circuit
• In this case, 5x causes a ―divide by
zero‖ error

Boolean Operators Example cont.

Dim x As Integer
x = 0
If x>2 AndAlso 5x > 1 Then ...
• This If statement is already false on
the x>2 part, so the AndAlso does
not check the 5x portion
• The key result: No Error!

The Value of True

• The value of True has not changed
• Originally, the value of True was going
to change, but it did not
• The value of True in VB .NET is still
negative one (-1)
• Your code should not check for -1,
but for True

Common Language Runtime

• VB.NET has undergone a significant
overhaul to accommodate the CLR
• New object oriented design features
• Much higher levels of type safety
• Universal type system allows for greater
inoperability

Changes in Properties

• The Alignment property becomes
TextAlign
• The maximum length of identifiers is
16,383
• All new Help — MSDN
• OptionButton becomes RadioButton
• Frame becomes GroupBox
• New component tray holds non-visible
controls

More Property Changes
• Text boxes have a Clear method
txtName.Clear()
txtName.Text = ―‖
• Focus method replaces SetFocus
txtName.Focus()
• Many colors available through the Color
class
• lblMessage.ForeColor = Color.Blue
Color.Aquamarine
Color.Bisque
Color.Chocolate
Color.Cadetblue

Tab Order
This is neat! Click on View and Tab
Order

Caption / Text Property
• VB 6.0 - Some controls, such as
Label, have a Caption property that
determines the text displayed in or
next to the control. Other
controls, such as TextBox, have a
Text property that determines the text
contained in the control
• VB.NET - In Windows Forms, the
property that displays text in a
control is consistently called Text on
all controls. This simplifies the use of
controls.

VB.NET IDE

• Form Window
• form window default name is Form1
• Here you add controls to create the user
interface.
• Toolbox
• contains the controls used to build the
user interface

VB.NET IDE

• Solution Explorer
• contains a list of files and forms in your
project
• Properties Window
• list of properties for each control.
• The column on the left contains the
names of the properties for that control.
• The column on the right contains the
settings for the properties.

VB.Net IDE
• Naming Controls
• Controls are identified by their names
• Rules for naming controls
• Names must start with a letter.
• name can contain any combination of
letters, numbers, or underscores ( ).
• Name Cannot contain spaces.
• Avoid using any special characters.
• Names can be more than 1,000characters
but limit it with twenty characters.
• start all controls with a three-character
prefix to identify the type of control

VB.Net IDE – Naming Controls

VB.Net IDE

• Code Window
• Where the program code is written
• To view right click on the form and
select View Code object the popup or
double-click on the object
• Example
• Double-click on the Button
• That opens the Code Window and creates a
procedure and will create event

VB.Net IDE

• Code Window
• procedure is a block of code that
completes a particular task.
Private Sub
…
End Sub.
• Event
• When you double-clicked on the Button,
it created a click event for that Button

Data Types

byte 1 byte Range Unsigned
0 to 255 byte
sbyte 1 byte Range Signed
-128 to 127 byte
Short 2 Range Signed
(sho) bytes -32768 to 32767 short
ushort 2 Range Unsigned
bytes 0 to 65535 short

More Integer Data Types
int 4 bytes Range Signed
-2,147,483,647 to
(int) 2,147,483,647 integer
uint 4 bytes Range Unsigned
0 to 4,294,967,295
integer
long 8 bytes Greater than Signed
(lng) 900,000 trillion long int
ulong 8 bytes Greater than 18 Unsigned
million trillion long int

Other Data Types
single 4 Range Float
(sng) bytes A number 6 digits past number
the decimal
double 8 Range Double
(dbl) bytes A number 14 digits past precision
the decimal
decimal 8 Range Fixed
bytes A number 28 zeros long precision

string (str) N/A Range N/A Unicode
char 2 Range Unicode
bytes 0x0000 to 0xFFFF character

Bool (bln) True or False Boolean

Converting Data Types
• Initialize a variable at declaration
Dim intMax As Integer = 100I
Dim decRate As Decimal = 0.08D
• Declare multiple variables at once
Dim intCount, intNum As Integer
• Convert all input to correct data type
(Do not use Val function)
decSale = CDec(txtSale.Text)
• CInt (still rounds to even #)
• CDec
• CStr
** CInt and CDec parse some characters
like $, commas,()

Format

• VB 6.0 –
Format(variable, ―Currency‖)
• VB.NET – FormatCurrency(variable)
FormatPercent(variable)
FormatNumber(variable)
FormatNumber(variable,3)
FormatDateTime(variable)

Changes in Syntax
• Currency
• Replaced with Decimal in VB.NET
• The Currency data type (64 bit) does not
provide sufficient accuracy to avoid
rounding errors, so Decimal (96 bit) was
created as its own data type.
• Dim x As Currency
is upgraded to:
Dim x As Decimal

Long and Integer Data Types

• VB 6.0 - Long variables were stored
as 32-bit numbers and Integer
variables as 16-bit numbers
• VB.NET - Long variables are stored
as 64-bit numbers, Integer variables
are stored as 32-bit numbers, and
Short variables are stored as 16-bit
numbers.

Variant Data Type
• From Variant data types to Object
• due to keeping all the languages more similar.
This is no longer the same as a pointer to an
object.

• Dim x As Variant

is upgraded to:

Dim x As Object

Object Data types

• Object supports all classes in the .NET
Framework class hierarchy and
provides low-level services to derived
classes. It is the root of the type
hierarchy.
• Everything inherits from Object-everything.
• The Object data types make VB.NET
better but they also make your
programming easier.

Object Data types

• 7 methods of Object:
• Equals(Object) as Boolean
• Equals(Object, Object) as Boolean
• GetHashCode() as Integer
• GetType() as System.Type
• New()
• ReferenceEquals(Object, Object) as
Boolean
• ToString() as String

Object Data types

• If you look at another data type such as
Char in the VB.NET Object Browser,
you'll see six of the seven methods are
also available.
• The missing one is the constructor
method, New(). This is taken care of
when a variable is declared.

Object Data types

• VB 6.0
• If (UCase(chrl) >= "A" And UCase(chrl)
<= "Z") Then ...
• to find out if a one character string is actually a
letter.
• VB.NET,
• If Char.IsLetter(myCharVar) Then ...

Option Explicit

• Option Explicit { On | Off }

• In VB.NET the option is turned on by
default for all new projects.
• When Option Explicit Off is used (not
a good programming style), you can
use any variable without first
declaring it.

• To Set
1. On the Tools menu, choose Options.
2. Open the Projects and Solutions node.
3. Choose VB Defaults.
4. Modify the Option Explicit setting.
5. To set Option Explicit on the command
line
6. Include the /optionexplicit compiler option
in the vbc command.

• Example
• In this example Option
Explicit statement use to force explicit
declaration of all variables. Attempting
to use an undeclared variable causes
an error at compile time.

Force explicit variable declaration.

• Option Explicit On

• Dim thisVar As Integer thisVar = 10
thisInt = 10 ' causes ERROR

Option Strict On
• New Option in VB.NET
• When Option Strict is turned on, the
compiler/editor does not allow implicit
conversions from a wider data type to a
narrower one, or between String and
numeric data types
• When you use the Option Strict statement,
the statement must appear before any other
code

Option Strict On
• Option Strict also generates an error
message in the following scenarios:
• For any undeclared variable. This is
because Option Strict also implies Option
Explicit.
• Late binding.

• If Option Strict is Off we can convert the
value of Long to an Integer.
• Limits erroneous numbers or run-time
errors

Option Strict On
• Example
• Option Strict On
Public Class Form1

Private Sub Button1_Click(ByVal sender As
System.Object, _ ByVal e As
System.EventArgs) Handles Button1.Click

Dim longNum As Long Dim intNum As
Integer longNum = 12345 intNum =
longNum MsgBox(intNum)
End Sub
End Class

Case Conversions

• String ToUpper and ToLower methods
• Replace UCase and LCase functions
• If txtInput.Text.ToUpper = ―YES‖

New Compound Operators

• New assignment Operators
• += –= *= /= = &=
• decTotal += decSale same as
decTotal=decTotal + decSale

Creating variables

• Variable
• a storage container for your data
• Declaration –creation of variable or
declaring a variable
• Assignment – change the value in a
variable
• Syntax
• Dim varName As Type
• Declaration Example
• Dim shoTest as Short

Creating variables

• Variable
• initializing a variable
• You must initialize a variable at the same
time you declare it
• Example
• Dim shoCaseSize As Short = 24
• Dim strLastName As String = "Jefferson―

Remember : When you assign a value
to a variable, you must make sure it
can store the answer

Creating variables

• Different assignment of variable
• Use an assignment statement to place a
value in a variable
• shoTestScore = 88
• assigning the value of one variable to
another
• strNewAddress = strOldAddress
• using a mathematical equation
• shoTotal = shoNum1 + shoNum2
• shoTotal = shoNum1 + 10

Rules of Precedence

• what’s in parentheses first and work
your way out,
• exponentiation before other
mathematical calculations,
• multiplication and division from left
to right, and then
• addition and subtraction from left to
right.

Rules of Precedence

• Example
• sngAverage = (shoTest1 + shoTest2 +
shoTest3 + shoTest4)/4
• 175=3
• 17 Mod 5 = 2
• 17^5

Creating Constants

• Constants are like variables except
their values cannot be changed while
the program is running
• Example
• Const sngSalesTaxRate As Single = 0.05
• Const strTitle As String = "A Tale of Two
Cities"

Creating Constants

• What is wrong with each of the
following?
• shoNum + shoNum2 = shoTotal
• shoNum = 10∗4
• Dim decPrice As Decimal = "$4.99"
• shoCube = (shoSide)3

Block-Level Scope

• VB .NET introduces variables that
only exist within blocks of code
• Blocks are items such as
For…Next, Do…Loop, and If Then…End
If
• Variables are only visible within the
block, but their lifetime is that of the
whole procedure

Block-Level Scope

• For Loop
• enable us to execute a series
of expressions multiple numbers of
times. For loop needs a loop
index which counts the number of loop
iterations as the loop executes.

For loop

• syntax
• For index=start to end[Step step]
[statements]
[Exit For]
[statements]
Next[index]
• Example
Dim i As Integer
For i = 1 To 10
Console.WriteLine(i)
Next

Do.. Until

• Do...UNTIL Loop
• is a loop that runs until the loop's condition
is true, the condition being checked after
each iteration of the loop.
• Syntax
• Do
statements
Loop Until condition

Do.. Until

• Example
Do Until i > 10
i=i+1
Loop

Do...Loop While

• Do… While loop:

A Do...Loop While loop runs until the
loop's condition becomes false. Its
condition is checked after each iteration
of the loop.

Do...Loop While

• Syntax
• Do
statements
Loop While condition
• Example Shows the DO while Loop:
Do
i=i+1
Loop While i < 10

Arrays
• VB 6.0 - Arrays can be defined with lower
and upper bounds of any whole number.
The Option Base statement is used to
determine the default lower bound if a
range is not specified in the declaration.
• VB.NET- To enable interoperability with
other languages, all arrays must have a
lower bound of zero. This makes the
Option Base statement no longer
necessary.
• Dim a(1 To 10) As String
is upgraded to:
Dim a(10) As String

Array Size

• This is one area that was going to
change, but did not
• When you declare an array, it starts at
zero, and the element number you use
is the Upper Bound of the array
• This means that arrays will always be
one larger than the size declared
• Dim x(2) As Integer has three
elements

While Loops
• VB 6.0 - While statements are ended with
a WEND statement.
• VB.NET - WEND statements are changed
to End While. This improves language
consistency and readability.
• It executes a block of statement as long as
condition is true.

While Loops

• syntax:
• While condition
statement-block
End While
• Example
While i < 10
i = i + 1 // same with i+=1 or i++
End While

Arrays Continued

• Arrays in VB.NET are classes
supporting properties and methods,
making them quite flexible.
• .Sort
• .Reverse
• You can sort an array in one line of
code!

VB 6.0 to VB.net

OTHER CHANGES

Parameter Passing
• VB 6.0 - Parameters that do not
specify either ByVal or ByRef default
to ByRef
• VB.NET - Parameters that do not
specify either ByVal or ByRef default
to ByVal. Defaulting to ByVal rather
than ByRef eliminates the problem of
having a procedure mistakenly
modify a variable passed in by the
caller.

GoSub, On Goto

• VB 6.0 - The GoSub line ... Return
statement branches to and returns
from a subroutine within a
procedure.
• VB.NET - GoSub...Return is a
nonstructured programming
construct. Its use makes programs
harder to read and understand.
Creating separate procedures that
you can call may provide a more
structured alternative or use case
statements.

Structures Replace UDTs

• User Defined Types (UDTs) have
been replaced with Structures
• Structures are far more powerful
than UDTs
• They support the equivalent of
properties and methods
• They are not as powerful as classes

File I/O Changes

• VB .NET supports such built-in
functions as FileOpen and Write
• These functions are found in the
Microsoft.VisualBasic namespace
• VB6 code that is upgraded to VB
.NET will use these functions
• The Framework includes a rich
namespace called System.IO

The System.IO Namespace

• System.IO contains a large number
of classes for handling all types of
I/O
• There are a variety of major
categories of objects in System.IO
• These include objects to manage files
and directories, read and write text
files, and read and write binary streams

Working with Files

• FileInfo and DirectoryInfo
classes are for such operations as
creating, moving, and deleting files
and directories
• If you use the Open method of
FileInfo to open a file, the returned
object is a FileStream

Reading and Writing Files

• The StreamReader and
StreamWriter classes are common
ways to perform file I/O
• This can read binary and text data
• The StringReader and StringWriter
are designed to read text data

Structured Error Handling

• VB .NET now supports Structured
Exception Handling (SEH)
• On Error Goto is still supported
• SEH uses the Try…Catch…Finally
syntax
• Should help reduce spaghetti code

Overloading

• Overloading is the ability to have the
same method, but with different
arguments
• You could fake this in VB6 using
ParamArrays
• For example, a FindCustomer
method could accept a customer ID,
a customer name, or a contact name

Constructors and Destructors

• Constructors are blocks of code that
run when a class is instantiated
• Destructors are blocks of code that
run when a class drops out of
memory
• Constructors can be overloaded to
make them more powerful
• Due to garbage collection, you
cannot be assured of when
destructors will execute

Dispose and Finalize

• Finalize will run when the object is
cleaned up by the GC
• You might want to release resources
explicitly, since you cannot
determine when Finalize will be
called
• Use the Dispose design pattern to
explicitly free resources

Multithreading

• VB .NET allows you to create truly
multithreaded (or free threaded)
applications
• The Framework includes a
System.Threading namespace to
make working with threads easier
• You will learn more in Chapter 11,
―Multithreaded Applications‖

Activity #1

TUITION CALCULATOR

Activity # 1 - Tuition Calculator

• TuitionCalculator Code
• Public Class frmTuitionCalculator
• Private Sub btnExit_Click(ByVal sender As System.Object,
• ByVal e As System.EventArgs) Handles btnExit.Click
• End
• End Sub
• Private Sub btnTuition_Click(ByVal sender As
• System.Object, ByVal e As System.EventArgs) Handles
• btnTuition.Click
• Dim shoCredits As Short
• Dim decTuition As Decimal
• shoCredits = txtCredits.Text
• decTuition = shoCredits * 100
• lblTuition.Text = decTuition.ToString
• End Sub
• End Class

Errors in Your Program
• Syntax errors
spelling or usage errors in your code.
Computer doesn’t understand what
you’ve written.
• Logical errors
• errors in your thinking. The computer
understands the commands, but the
―what to do‖ or ― how to do them‖ is
different than what you were expecting.
• Runtime errors
• Problems that crash a program.

Creating Vb. Simple program

VB.NET AT WORK


• Procedure for creating the program
• Form Window
1. In every System you must first to create the
user interface and add all the control needed
2. name all the controls
3. Choose the control that will trigger the event
and go to code window

Note: Design should follow later after the
program works


• Procedure for creating the program
• Code Window

Object Oriented Programming I

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