vb3 oop prac

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Object Oriented ProgrammingUsing Visual Basic

Lab Guide

The Practicals

1-1: Creating a Student Class

1-2: Adding a parameterised constructor

1-3: Enumerated Types

1-4: BankTeller Application

1-5: Manually testing integer input

OOP Lab

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1-1: Creating a Student Class

1-2: Adding a parameterised constructor

Lab3

OOP Lab

Lab 1-1: Creating a Student class

You will create a two-tier application that usesa form to passinputs by the user to the Student class.

The presentationtier:

the formsclass

The middle tier:

theStudentclass

The formwill have controlsallowing the user to input a StudentID, last name, and test average.

When the user clicks a button, your code will assign the inputvaluesto Student classproperties.

The formwill also have a label to redisplay the Student object.

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Lab 1-1

The formafter the user clicks theSave button.

The same form af ter the user clicks

the View button.

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Lab 1-1 Steps

Step1:

Create a new Windows application named Student ClassExample.

Step2:

Next, add a classnamed Studentto the project.

Right-clickon theProjectname,selectAdd, and selectClass.

In the Add New Itemdialog window, select Code, selectClass, and enter the classname asStudent.vb.

Step3:

Open the Student.vb file and replace its contents with the

classdefinition in the next slide: OOP Lab

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Lab 1-1 Steps

Public Class Student

Public Property IdNumber As String auto-implemented property

Public Property LastName As String auto-implemented property

Private mTestAverage As Double

The TestAverage property requires range checking,

so it is implemented with explicitGet and Set sections.

Public Property TestAverage As Double

Get

Return mTestAverage

End Get

Set(ByVal value As Double)

If value >= 0.0 And value


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Lab 1-1 Steps

Next, you will write code in the startup form that copies theusers inputs to Student properties.

Step5:

Declare a Student variable at the classlevel (inForm1):

Private objStudent As New Student

Step6:

Create theClickhandleronthenext slide for the Savebutton.

Youcanomit the parametersfrom the btnSave_Click procedure becausethey are optional

NB: Relaxed delegates is a VB feature that allows you to omit

parameters in event handlers if the parameters are not being used

insidethe body of thehandler.

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Lab 1-1 Steps

Public Class Form1

Private objStudent As New Student

Private Sub btnSave_Click() Handles btnSave.Click

objStudent.IdNumber = txtIdNumber.Text

objStudent.LastName = txtLastName.Text

objStudent. TestAverage= CDbl(txtTes tAverage.Text)

lblStudent.Text = "(student information saved)"

End Sub

End Class

Copies values from the TextBox controls into the propert ies of the objStudentobject.

lblStudentis addedto providea hint to the user.

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Lab 1-1 Steps

Step7:

Create a Clickhandler for the View button that usesthe Student.ToStringmethod to display the Studentobject:

Private Sub btnView_Click() Handles btnView.Click

lblStudent.Text = objStudent.ToString()

End Sub

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Lab 1-1 Test

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Step 8:Save the project, and run the application with thefollowing test:

Input Expectedoutput

Enter an ID number such as001234, a students last name,and a 0 for average and click theSavebutton.

Thenclick theViewbutton.

You should see the same IDnumber and name that youentered.The test average will display as

value 0.


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Lab 1-2

Adding a parameterised constructor to the Studentclass

Threeparameters:

1. ID number,

2. last name,

3. test average

The application will ask the user to input values,whichare thenpassed to theStudent constructor.

Then the application will display the values storedinside theStudent object.

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Lab 1-2: Adding a ParameterisedConstructor to the Student Class

Step1:

In Windows Explorer, make a copy of thefolder containing the Student Class Exampleproject you wrote for Lab1-1.

Openthe new project.

Step2:

Change the caption in the forms title bar toStudent Classwith Constructors.

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Step3:

Add thefollowing constructor to theStudent class:

Public S ub Ne w(By Val pIdN umber As Str ing,

Optional ByVal pLastName As String = "", Optional

ByVal pTestAverage As Double = 0.0)

'the secon d a nd t hird pa ram ete rs are

optional

IdNumber = pIdNumber

LastName = pLastName

TestAverage = pTestAverageEnd Sub

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Step4:

Edit the forms source code. First, change thedeclarationof objStudent to the following:

Private objStudent As Student

Thisstatement declares a Student variable, but it doesnot create a studentObject.

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Step5:

Modify the btnSave_Click event handler so it contains thefollowing code:

Private Sub btnSave_Click() Handles btnSave.Click

Dim testAverage As Double

If Double.TryParse(txtTestAverage.Text, testAverage) Then

objStudent = New Student(txtIdNumber.Text,

txtLastName.Text, testAverage)

calls the Student constructor, assigning values to the three class

variables.

lblStudent.Text = "(student information saved)"

Else

lblStudent.Text = "Test average is not a valid number"

End If

End Sub OOP Lab

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Lab 1-2: Test the app

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Input Expectedoutput

Enter 200032, Odhis, 92.3 in the3 textboxes and click the Savebutton.Thenclick theView button.

You should see the same IDnumber, name and average thatyouentered.

Enter 100011, Ali, XX in the 3textboxes and click the Savebutton.

You should see the same IDnumber and name you entered,and an error message in thelabel.

1-3: Enumerated Types

1-4: Bank Teller Application

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OOP Lab

Lab 1-3

Enumerated Account type

When the user selects an account type f rom a list box,the selected index is converted into an AccountTypeobject.

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1.4Bank Teller Application

Two-tier application that simulates an electronicbankteller

user looks up account, deposits & withdraws funds,viewsthebalance

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Requirements

1. User looks up existing account information byentering an Account number (ID).

2. If the account exists, the account name and balanceare displayed.

3. User can enter an amount to deposit into theaccount.Thisdeposit is added to the balance.

4. User can enter an amount to withdraw from theaccount. If the amount is


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1-5: Manually testing integer input

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OOP Lab

Requirements Specification

The application prompts the user with a range of acceptableinteger values.

The user inputs an integer N.

If N is a noninteger value, the application displays an errormessage.

If N is outside the range of acceptable values, the applicationdisplaysan error message.

If N is within the range of acceptable values, the applicationdisplaysthe name of a color that matchesN fromthe followinglist: 0 = white, 1 = yellow, 2 = green, 3 = red, 4 = blue, 5 =orange.

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Lab 1-5

Manually testing integer input

Displays a string by using the input value as asubscript intoan array of strings

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Testing Plan

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