VB.Net Introduction

.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

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.

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)

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, solution explorer, 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

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

Typical VB.Net Controls

• Form design view: ToolBox/Windows Forms– TextBox– Label– Button– CheckBox– RadioButton– ListBox– ComboBox– PictureBox– Etc.

Form

• Properties:– Name, FormBorder, Text, BackColor, BackImage,

Opacity?

• Events:– Load, Closed

• Rename a form(hard to to):– Change the name and text property.– Rename the form in the Solution Explorer.– Change the StartUp in the Project Property.– Change the name in the code window.

Text Box• Properties:

– AutoSize, BorderStyle, CauseValidation, Enabled, Locked, Multiline, PasswordChar, ReadOnly, ScrollBar, TabIndex, Text, Visible, etc.

• Events:– CauseValidation, TextChanged, etc.

• To refer to a property: – ControlName.PropertyName– Ex. TextBox1.Text

• Properties can be set at the design time or at the run time with code.– Demo: TextAlignment

• Label – Display message, output– Property:– Text, TextAlign– Autosize– Visible

• Button– Click event

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.

Demo

Num1

Num2

Sum =

Control propertiesEvent: Click, MouseMove, FormLoad, etc.Event proceduresSum: textBox3.text=CStr(CDbl(textBox1.text)+CDbl(textBox2.text))Or (CDbl(textBox1.text)+CDbl(textBox2.text)).toStringChallenge: How to draw a horizontal line?

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.

Configure VB Project

• Project property page– General– Build:

• Option Explicit: On – must declare variables

• Option Strict: Off – VB will automatically convert data if necessary

• Option compare: Binary – case sensitive

– Imports

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

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.

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

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

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

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 (variable declared in a Module) declared with the Public keyword.

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

• Ex. System.Convert.ToDateTime(var)

• Type class’s methods:– toString

• Demo: Val

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#

• 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)

• Date data type format methods

Some Date Functions

• Now: Current date and time

• Today: Current date

• TimeOfDay

• DateDiff

• Demo– Days to Christmas– Date data type properties and methods

Arithmetic and String Operators• +, -, *, / , ^, ( )• \:Integer division

– Return integer result– If the operands are real numbers, they are rounded to the

nearest whole number before the division takes place.

• Mod:– Remainder = 17 mod 5

• Order of evaluation:– 1. ( ), 2. ^, 3.*, /, 4.\, 5.Mod, 6.+, -

• String Concatenation: &, +• Compound operator:

: X= X+1 or X +=1

Demo

• Chap 3, simple calculator