Introduction to VB.Net By William Lacktano.ppt

Introduction to VB.Net By William Lacktano Visual Basic Presentation

1. VB.Net Introduction
RCCS 307
BY W. LACKTANO

2. .NET Framework
•.NET Framework class libraries: A large set
of classes that forms the basis for objects
that can be used programmatically.
–Programming in the .NET Framework means
making use of the classes exposed by the
Framework, building your own classes on top
of these and manipulating the resulting objects.
•Creating Internet applications and Windows
applications

3. Class and Object
•A class is a blueprint from which objects
are made. Every object created from a
class is an instance of the class.
•Properties and methods: An object’s
interface consists of properties and
methods. A property is an attribute
associated with an object, while a method is
an action that the object can carry out.

4. VB.NET is Object-Oriented
•Everything from the simplest data types
provided by VB to the complex windows is
a class.
–Ex:
•Dim iNum as Integer
•iNum=10
•Debug.WriteLine (“The number is: “ &
iNum.ToString)

5. Visual Studio .NET
•It is the development environment for creating
applications based on the .NET Framework.
•It supports VB, C#, and C++.
•Demo:
–Start page: MyProfile
–Starting project: Project types, name and location,
–Solutions and projects, renaming a project, property
page, AutoHide, Dock/Float
–Configure start up environment: Tools/Option
–View/Solution, View/Class, Project/Add Windows
Form, Project/Add New Item
–Form, Code view, File Properties and Object properties

6. Introduction to Visual Basic .Net
•Event-driven programming
–The interface for a VB program consists of one
or more forms, containing one or more controls
(screen objects).
–Form and control has a number of events that it
can respond to. Typical events include clicking
a mouse button, type a character on the
keyboard, changing a value, etc.
–Event procedure

7. Typical VB.Net Controls
•TextBox
•Label
•Button
•CheckBox
•RadioButton
•ListBox
•ComboBox
•PictureBox

8. Text Box
•Properties:
–AutoSize, BorderStyle, CauseValidation, Enabled,
Locked, Multiline, PasswordChar, ReadOnly,
ScrollBar, TabIndex, Text, Visible, etc.
•Properties can be set at the design time or at the
run time using codes.
•To refer to a property:
–ControlName.PropertyName
–Ex. TextBox1.Text

9. Typical VB.Net Programming
Tasks
•Creatin g the GUI elements that make up
the application’s user interface.
–Visualize the application.
–Make a list of the controls needed.
•Setting the properties of the GUI elements
•Writing procedures that respond to events
and perform other operations.

10. Demo
Num1
Num2
Sum =
Control properties
Event: Click, MouseMove, FormLoad, etc.
Event procedures
Sum:
textBox3.text=CStr(CDbl(textBox1.text)+CDbl(textBox2.text))
Or (CDbl(textBox1.text)+CDbl(textBox2.text)).toString
Challenge: How to draw a horizontal line?

11. VB Projects
•A VB project consists of several files. Visual
Studio .Net automatically creates a project folder
to keep all project files in the folder.
–Solution file
–Project file
–Form file
–Modules
–Class file
–Etc.

12. Configure VB Project
•Project property page
–General
–Build: Option Explicit
–Imports
•Debug
–Debug/Windows

13. Introductory VB Topics
•Declaring variables: Option Explicit
–DIM, PUBLIC, PRIVATE, STATIC, CONST
–Boolean, Integer, Long, Single, Double, Date,
String
–Ex: DIM dblIntRate As Double
–Ex: Dim X As Integer, Y As Single
–Ex: Dim A, B, C As String
–Ex: Dim X AS Integer = 25
–Ex: CONST Maximum As Integer = 100

14. Variable Declarations
•Dim variableName as DataType
•Variable naming rules:
–The first character must be a letter or an underscore
character.
–Use only letters, digits, and underscore.
–Cannot contain spaces or periods.
–No VB keywords
•Naming conventions:
–Descriptive
–Consistent lower and upper case characters.
•Ex. Camel casing: lowerUpper, employeeName

15. Control Naming Conventions
•The first three letters should be a lowercase prefix
that indicates the control’s type.
–frm, txt, lbl, btn.
•The first letter after the prefix should be
uppercase.
–txtSalary, lblMessage
•The part of the control name after the prefix
should describe the control’s purpose in the
application.

16. VB Data Types
•Boolean (True/False):2 bytes
•Byte: Holds a whole number from 0 to 255.
•Char: single character
•Date: date and time, 8 bytes.
•Decimal: Real number up to 29 significant digits, 16 bytes
•Double: real, 8 bytes
•Single: real, 4 bytes
•Integer: 4 bytes(int32, uint32)
•Long: 8 bytes integer
•Short: 2 bytes integer
•String
•Object: Holds a reference of an object

17. Variable Declaration Examples
•Dim empName as String
•Declare multiple variables with one Dim:
–Dim empName, dependentName, empSSN as String
•Dim X As Integer, Y As Single
•Initiatialization
–Dim interestRate as Double = 0.0715

18. Variable Default Value
•Variables with a numeric data type: 0
•Boolean variables: False
•Date variables: 12:00:00 AM, January 1 of
the year 1.
•String variables: Nothing

19. Object Reference
•Declare object variales:
–Dim varName As Classname
–varName = New Classname()
–Or: Dim varName As New Classname()
•Dereferencing objects:
–varName = Nothing

20. Variable Scope
•Block-level scope: declared within a block of code
terminated by an end, loop or next statement.
–If city = “Rome” then
•Dim message as string = “the city is in Italy”
•MsgBox(message)
–End if
•Procedural-level scope: declared in a procedure
•Class-level, module-level scope: declared in a
class or module but outside any procedure with
either Dim or Private keyword.
•Project-level scope: a class or module variable
declared with the Public keyword.

21. Data Conversion
•Implicit conversion: When you assign a value of
one data type to a variable of another data type,
VB attempts to convert the value being assigned to
the data type of the variable if the OptionStrict is
set to Off.
•Explicit conversion:
–VB.Net Functions: CStr, Ccur, CDbl, Cint, CLng,
CSng, Cdate,Val, etc.
–.Net System.Convert
•Type class’s methods:
–toString

22. Date Data Type
•Variables of the Date data type can hold both a
date and a time. The smallest value is midnight
(00:00:00) of Jan 1 of the year 1. The largest
value is 11:59:59 PM of Dec. 31 of the year 9999.
•Date literals: A date literal may contain the date,
the time, or both, and must be enclosed in #
symbols:
–#1/30/2003#, #1/31/2003 2:10:00 PM#
–#6:30 PM#, #18:30:00#

23. •Date Literal Example:
–Dim startDate as dateTime
–startDate = #1/30/2003#
•Use the System.Convert.ToDateTime
function to convert a string to a date value:
–startDate = System.Convert.ToDateTime(“1/30/2003”)
–If date string is entered in a text box:
•startDate = System.Convert.ToDateTime(txtDate.text)
•Or startDate=Cdate(txtDate.text)

24. Arithmetic and String Operators
•+, -, *, /. \, ^
•String Concatenation: &, +
•Compound operator:
: X= X+1 or X +=1

25. IF Statement
•IF condition THEN
statements
[ELSEIF condition-n THEN
[elseifstatements]
[ELSE
[elsestatements]]]
End If

26. Select Case Structure
•SELECT CASE testexpression
[CASE expressionlist-n
[Statements]
[CASE ELSE
[elsestatements]
END SELECT

27. Select Case Example
•SELECT CASE temperature
CASE <40
Text1.text=“cold”
CASE 40 to 60
Text1.text=“cool”
CASE 60 to 80
Text1.text=“warm”
CASE ELSE
Text1.text=“Hot”
End Select

28. Loop
•FOR index –start TO end [STEP step]
[statements]
[EXIT FOR]
NEXT index
DO [{WHILE| UNTIL} condition]
[statements]
[EXIT DO]
LOOP

29. Do While/Do Until
Private Sub Command1_Click()
Dim counter As Integer
counter = 0
Do While counter <= 5
Debug.Print counter
counter = counter + 1
Loop
Text1.Text = counter
End Sub
Private Sub Command2_Click()
Dim counter As Integer
counter = 0
Do Until counter > 5
Debug.Print counter
counter = counter + 1
Loop
Text1.Text = counter
End Sub

30. With … End With
With TextBox1
.Height = 250
.Width = 600
.Text = “Hello”
End With
Convenient shorthand to execute a series of
statements on a single object. Within the block,
the reference to the object is implicit and need
not be written.

31. Procedures
.Sub procedure:
Sub SubName(Arguments)
…
End Sub
–To call a sub procedure SUB1
•CALL SUB1(Argument1, Argument2, …)

32. Function
•Private Function tax(salary) As Double
•tax = salary * 0.1
•End Function
–Or
•Private Function tax(salary)
•Return salary * 0.1
•End Function

33. Call by Reference
Call by Value
•ByRef
–Default
–The address of the item is passed. Any changes
made to the passing variable are made to the
variable itself.
•ByVal
–Only the variable’s value is passed.

34. ByRef, ByVal example
Private Sub Command1_Click()
Dim myStr As String
myStr = TextBox1.Text
ChangeTextRef (myStr)
TextBox1.Text = myStr
End Sub
Private Sub ChangeTextRef(ByRef strInput As
String)
strInput = "New Text"
End Sub