Vb.net Material

Prepared by: Noel Anonas

Visual Basic .NET


Day 1 Programming language syntax, declarations,

operators, statement, classes

Day 2 VB Form and Common Controls

Day 3 More VB Controls and other Features


Objectives of this Lesson

Elements in the Visual Studio Environment

(GUI)

Object-oriented programming

Concepts of classes, objects, properties,

methods and events


Programming Languages Overview

Procedural older, traditional, sequential

style

(Cobol, RPG, Pascal, etc.)

Event-Driven (Visual Basic 6.0 & earlier) Contain some elements of OOP but not all

Object-Oriented Programming (OOP) Visual Basic .NET (2005 or later)


OOP and VB.NET Objects have properties, methods and events

Each object is based on a class (a blueprint which all objects

are based upon)

Objects Examples Forms which are windows within the VB environment

Controls are components contained inside a form

Properties Examples Name (each object has a name )

Text ( what the user sees inside the control)

Methods Examples Open (methods perform an action)


Close

Events Examples User clicks a mouse button

User selects an item from a list

Classes

Classes are like blueprints ( or

templates) used to create objects

Classes contain the definition of all available

properties, methods and events for that

objects

Each new object created is based on a class


Creating three new labels makes each label an instance of the Label class

Object Model Analogy

A car belongs to the Car Class

The make, model, and color of the car are the

properties of the car

Each car is an object of the Car Class. This is

called an instance of the Car Class

When the car starts, stops or turns, these are

methods belonging to the Car.


An event occurs when the car pulls to the gas

station.

Objectives of this Lesson

Basic steps for writing a VisualBasic project

Explore the files that make up a Visual Basic

project

Define design time, run time and debug time

Error types: syntax errors, run-time errors and

logic errors

Launching Visual Basic .NET


Writing Visual Basic Projects

1. Design the UI (including the controls)

2. Set up the Properties for the controls

3. Code following the language syntax rules

Syntax Rules that MUST be followed such as

punctuation, spelling, use of special symbols

and keywords.


VB Application Files

Many files make up one VB application

Solution File (.sln) this is the one file that the

programmer interacts with. Avoid opening all

other files that are automatically created with

each solution!

Executable File (.exe) this is the file that the

end user ultimately runs (executes)


Various Modes of VB

Design Time used when designing the user

interface and writing code

Run Time used when running the application

(from the users perspective)

Break Time occurs when and error or other

condition occurs

More Terminology

Each user action causes an event to occur


Event procedures code written by the

programmer to react to events

VB will ignore events for which you don not write

code

Errors

Syntax Errors (must be fixed)

Sometimes called a compile error

VBs editor will detect and correct many

A blue squiggly line appears under code that

the editor does not understand


Mouse over the code to receive more details

The Error List window shows errors and more

details

Errors

Logic Errors (produces incorrect results)

Easy to overlook

Check calculations and other logic against

known test data results

VB editor can not detect logic errors


Debugging tools

Launch Visual Basic

Click Start

All Programs

MS Visual Studio 20xx

MS Visual Studio 20xx (again)

This will launch Visual Studio and we will now

be able to work with Visual Basic .NET within

Visual Studio


Launching VB Demo

DEMO Create a Console Application

Most commonly used VB function MsgBox()

InputBox()

Naming Rules

Begin with letters

No spaces

Avoid special symbols


Use camel casing Examples

messageLabel

exitButton

firstNameTextBox

Question Which of the following local variable names are allowed in VB, and which

have the correct style?

volume

AREA

Length

3sides


side1

lenth

Mysalary

your salary

screenSize

Dim

Answers: volume allowed, correct style;

AREA allowed, but area preferred;

Length allowed, but lower-case l preferred;

3sides not allowed, starts with a digit;

side1 allowed, correct style;

lenth allowed, even with incorrect spelling of length;


Mysalary allowed, but capital S is preferred;

your salary not allowed (no spaces allowed in middle of a

name);

screenSize allowed, correct style; Dim not allowed it is a

keyword.


Question

In the following, what are the values of the

variables after each statement?


Dim a, b, c, d As

Integer d = -8 a = 1 *

2 + 3 b = 1 + 2 * 3 c =

(1 + 2) * 3 c = a + b d

= -d


Double.Parse Sample String to number conversion

for arithmetic operation


Sample String to Number

Conversion


Sample Number to Number

Conversion

What is Operator

Operators determine behavior of statements


Exercise 1

Using Double types, write a program which converts a

Fahrenheit temperature to its Celsius (centigrade)

equivalent. The formula is:

c = (f - 32) * 5 / 9 Note:


Use InputBox() to get the fahrenheight value from the

user.

Display the value of c (centigrade)

Exercise 2 Calculate and display the series resistance, given by:

series = r1 + r2

and the parallel resistance, given by:

Use InputBox() to get the value or r1 and r2 from the user.

Use your calculator to check the output.


If Statement Sample


If Else statement


ElseIf keyword


IsNumeric() function

Exercise

Cinema (movie theatre) price

Write a program to work out how much a person pays

to go to the cinema. The program should input an


age from an InputBox() and then decide on the

following basis: under 5, free;

aged 5 to 12, half price;

aged 13 to 54, full price; aged 55, or over, free.

Exercise

Betting A group of people are betting on the outcome of three throws

of the dice. A person bets P1 on predicting the outcome of the

three throws. Write a program that uses the random number

method (VBMath.Rnd()) to simulate three throws of a die and

displays the winnings according to the following rules:


all three throws are sixes: win P20;

all three throws are the same (but not sixes): win P10;

any two of the three throws are the same: win P5.

Sample Using Date

Date syntax


Sample Using Date 2

Formatting the Date Display


Sample Using Date 3

Adding day and month

VB Windows Form

DEMO

Sample code using Windows Form


Demo


Output


Exercise The calculator Write a program which simulates a simple desk calculator (See Figure) that

acts on integer numbers. It has one button for each of the 10 digits, 0 to 9. It

has a button to add and a button to subtract. It has a clear button, to clear

the display, and an equals (=) button to get the answer.


When the clear button is pressed the display is set to zero and

the (hidden) total is set to zero.

When a digit button is pressed, the digit is added to the right

of those already in the display (if any).

When the + button is pressed, the number in the display is

added to the total (and similarly for the button).

When the = button is pressed, the value of the total is

displayed.

Exercise

Rock, scissors, paper game In its original form, each of the two players

simultaneously chooses one of rock, scissors or


paper. Rock beats scissors, paper beats rock and

scissors beats paper. If both players choose the same,

it is a draw. Write a program to play the game. The

player selects one of three buttons, marked rock,

scissors or paper. The computer makes its choice

randomly using the random number generator. The

computer also decides and displays who has won.


Select case sample


For Next / While


Do Loop

For Each


Exercise Saw-tooth pattern

Write a program to display a saw-tooth pattern, as

shown in a Figure, in a text box.


Use do loop statement.

Array

Array Data that is grouped together

into a collection of

information

Example: Telephone directory, flight schedule.

Sample Array

Array of Numbers


Array of Names

Array and indices


Creating an Array

Dim ages(5) As Integer indices going from 0 to 5.

Dim band(3) As String

Input a value for an element of an array: ages(2) =

CInt(TextBox1.Text) band(2) =

TextBox2.Text output

values: TextBox3.Text = "the first age is " & CStr(ages(0))

TextBox4.Text = "the 4th band member is " & band(3)


Length of an Array

Use of the Ubound() (upper bound) Dim length As Integer length = UBound(table)

Use of the Length

table.Length

ReDim

Array can be rebuilt to a different size using ReDim Dim table(19) As Integer

ReDim table(39)


Use Preserve as not to destroy the data: ReDim Preserve table(24)

Exercise - Array

Write a program that inputs a series of integers into an

array. The numbers are in the range 0 to 100. Calculate

and display: the largest number; the smallest number; the sum

of the numbers; the mean of the numbers. Apply looping (while or do statement) to store values into

array.


ArrayList

ArrayList - Dynamic array.

ArrayList Example:

Dim collection As ArrayList = New ArrayList()


ArrayList Properties & Methods

Properties

Count - The number of items in the array list.

Methods

Add -Add a new object to the array list. The new item is added at the end of

the list.

RemoveAt - Return and remove the object at the specified index from the

array list. Any remaining items are moved up to fill the gap created.

Remove - Remove the object from the array list.

Insert - Insert a new object into the array list at the index position specified.

Any items are moved down to make space for the new item. Parameters: index As Integer, newItem As Object

Clear - Empty the complete array list.


Exercise - ArrayList String ArrayList Write a program that uses an arraylist of 10 strings.

Write methods that carry out each of the following

operations: 1. Input values from the keyboard via a text box.

2. Display the values.

3. Input a word from a text box and search to see whether

it is present in the array.

4. Display a message to say whether it is present in the

array or not.


ListBox Adding Items to a list

ListBox1.Items.Add()

Removing Item from a list ListBox1.Items.RemoveAt(3)

Inserting items within a list ListBox1.items.Insert(5,tea)

Length of a List : ListBox1.Items.Count

Indices: ListBox1.selectedIndex

ListBox1.items returns an ArrayList


Exercise Write a program in which an item selected in a list box (by

clicking on it) is immediately deleted. Alternatively, provide a

'delete' button to delete the item that is currently selected.

Add another button so that items in the list box are

automatically sorted into alphabetical order.

Add a button that causes the list box to be emptied, using the

method Clear

Write a program that allows items to be inserted or removed

from any position within a list box, using suitable buttons.


Inserting single quote to a String

Use two quotes to stand for a single one: TextBox1.Text = "The word ""Object""" which displays:

The word "Object"

NewLine

End-of-line markers within a string. Imports Microsoft.VisualBasic.ControlChars


Dim s As String = "Tom" & NewLine & "Jerry" Or

vbCrLf

ToLower

string1 = "Version 1.1"

resultString = string1.ToLower()


ToUpper

string1 = "Basic"

resultString = string1.ToUpper()


Trim

string1 = " Center "

resultString = string1.Trim()


insert

This method lets us insert characters into a

string at a specified position, as in: string1 = "Visual programming"

resultString = string1.Insert(7, "Basic ") The result is "Visual Basic programming".

remove

This method removes a given number of

characters at a given position, as in:


string1 = "Deadline" resultString =

string1.Remove(1, 4) The result is "Dine"

Substring

string1 = "position"

resultString = string1.Substring(2, 3)

We have selected from s (which is at index 2)

for 3 characters, hence the result is sit.


Exercise

Palindrome

Write a program which inputs one string and

determines whether or not it is a palindrome.

A palindrome reads the same backwards and

forwards, so 'abba' is a palindrome. Assume

that the string contains no spaces or

punctuation.


Exception Handling

Try main task

Catch exceptionObject As FormatException display an error message

Catch exceptionObject As Exception Throw a new Exception

Throw new Exception(Wrong input)

Finally termination code

End Try


Exercise

Write a program which provides two textboxes for the

input of integer values a and b.

Display the result of a\b and b\a.

(Recall that \ performs integer division.) Incorporate exception handling for zero and

nonnumeric input textbox values.

File

Stream


a stream of data flowing in or out of the program

Note:

The file classes are in the System.IO namespace.

This is not automatically imported, so use: Imports System.IO

Read and write lines of text The ReadLine() of StreamReader.

This reads a whole line of text into a string, excluding the end-of-line

marker.

The WriteLine() of The StreamWriter class. This writes a string to a file.


The OpenText() and CreateText() of the File class. These are shared methods, and provide us with a new instance of a

text stream.

File Output Example ' write some lines of text to the file

Dim outputStream As StreamWriter = _

File.CreateText("c:\myfile.txt")

outputStream.WriteLine("This file will")

outputStream.WriteLine("contain 3")

outputStream.WriteLine("lines of text.")

outputStream.Close()

File input 'read the file line-by-line


Dim inputStream As StreamReader = _ File.OpenText("c:\myfile.txt")

Dim line As String line = inputStream.ReadLine()

While line Nothing

TextBox1.AppendText(line &

vbCRLF) line = inputStream.ReadLine()

End While inputStream.Close()

Using file dialogs

OpenFileDialog

Ex: If OpenFileDialog1.ShowDialog() = DialogResult.OK Then MessageBox.Show(OpenFileDialog1.FileName)

End If


Using file dialogs

SaveFileDialog

Ex: If SaveFileDialog1.ShowDialog() = DialogResult.OK Then MessageBox.Show(SaveFileDialog1.FileName)

End If

Exercise - File

Write a program which puts your name and

address in a file named address.txt. Use an editor to check that the file has the expected contents.


Write a program to count the number of lines

in a file. Ensure that it works for an empty file

(producing a value of zero).

Color Dialog

Demo for ColorDialog


Font Dialog

Demo for FontDialog


Exercise

Create a list of movies titles (5 movies) using

ListBox. Change the background color of the

list of movies to yellow and the foreground

color of the list to red.

Creating Splash Screen

Demo


Creating About Form

Demo


Creating a Menu

MenuStrip


Exercise - Menu

Create a Editor Menu that will implement the

following:

File Open, File Save, Welcome Screen, Help,

About and Exit

Creating a Module

Exercise

Write a program which produces a random

number between 200 and 400 each time a


button is clicked. The program should display

this number, and the sum and average of all

the numbers so far.

Use Random class

Creating a Class


Creating Constructor

Creating an instance

Exercise - Class

Bank account Write a program that simulates a bank account.

A text box allows deposits (a positive number) to be made into

the account and withdrawals (a negative number) to be made.

The state of the account is continually displayed and, if the

account goes into the red (negative balance), a suitable message

is displayed. Create a class named Account to represent bank

accounts. It has methods Deposit and Withdraw, and a property

Currentbalance.


Exercise Class 2

Scorekeeper Design and write a class that acts as a scorekeeper for a

computer game. It maintains a single integer, the score. It

provides a method to initialize the score to zero, a method to

increase the score, a method to decrease the score, and a

method to return the score. Write instructions to create a

single object and use it.

Creating Subroutine and Function

Demo


Exercise

Balloons Add to the class Balloon some additional data, a String

that holds the name of the balloon and a variable

that describes its colour. Add code to initialize these

values using a constructor method and add the code

to display them.

Enhance the balloon program with buttons that move

the balloon left, right, up and down.


Timer

Properties

Enabled Set to True to switch the timer on. Interval The

frequency of Tick events in milliseconds (1/1000

seconds).

Events

Tick

Called when the timer ticks every Interval milliseconds.

Graphics


Graphics Constructor

Created from a picture box object using CreateGraphics. For

example:

Dim paper As Graphics = PictureBox1.CreateGraphics() Methods

Clear - Clear the graphics area and fill it with the colour provided

as the parameter.

DrawLine - Draw a line. Parameters: myPen As Pen, x, y, width, height

DrawEllipse -Draw an ellipse. Parameters: myPen As Pen, x, y, width, height


DrawImage - Draw an image. Parameters: myImage As Image, x, y, width, height

Graphics Methods:

DrawRectangle - Draw a rectangle. Parameters: myPen As Pen, x, y, width, height

FillEllipse - Draw a filled ellipse. Parameters: myBrush As SolidBrush, x, y, width, height

FillRectangle - Draw a filled rectangle. Parameters: myBrush As SolidBrush, x, y, width, height


Sample

Dim paper As Graphics

paper = PictureBox1.CreateGraphics() Dim

myPen As Pen = New Pen(Color.Black)

paper.DrawRectangle(myPen, 10, 10, 100, 50)

paper.DrawRectangle(myPen, 10, 75, 100,

100)

Exercise Steps Write a program to draw a set of

steps made from bricks, as shown in Figure.


Use the library method DrawRectangle to

draw each brick.

(Use for loop)

Exercise -

Graphics 1 Write a program which displays

changing minutes and seconds,

representing them by two long

rectangles: make the maximum width of the rectangles equal

to 600 pixels to simplify the arithmetic (10 pixels for each

minute and each second). Redraw the two rectangles every


second. The Figure shows a representation of 30 minutes and

15 seconds.

Exercise

Scorekeeper


Design and write a class that acts as a

scorekeeper for a computer game. It

maintains a single integer, the score. It

provides a method to initialize the score to

zero, a method to increase the score, a

method to decrease the score, and a method

to return the score. Write instructions to

create a single object and use it.

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