APPLICATIONS DEVELOPMENT

Using VB .NetNote:

The prerequisites of this course are CMP218 or CMP219 or ITE204 and

concurrent requisite of CMP252 or ITE252

Learning new languages

Computer Programming Languages

Can be classified into two basic types Object Oriented Programming Procedural Programming

Each computer language classified under each “type” will follow specific guidelines.

knowing the specific guidelines within a language type will help in learning the different languages within each type.

Computer Programming Languages (Continued)

Procedural Languages Examples include

PASCAL C COBALD

Follow a top down design Object Oriented Languages

Follow OOD (Object Orient Design) Examples include

C++ Java VB .Net

Object Oriented Languages Overview (Review questions)

Some questions that should be answered as a review. What is OOP (Object Oriented Programming)? What are Data Types (Primitive and Abstract)? What is the String Data Types and its associated methods? How do you convert numeric data from a String to a Primitive data type? What is the difference between a class and an object? What are attributes? What are methods?

What is a constructor? What is an Accessor? What is a Mutator/Modifier?

What is inheritance? What are loops? What is Exception Handling and Why is it used? What does public and private mean? What are control structures (if and switch statements) What are the following operators

Assignment? Math? Comparison/Logical? Boolean?

Classes in OOP Are object descriptions Contain both attributes and methods

Attributes are data types that describe the object Can be both Primitive data types and other classes Can be public or private

Methods are the actions that the object can do Three types of methods

Constructor Accessor Mutator/Modifier

Every method contains a specific format Every method contains an accessibility (public/private) Every method contains a parameter lists (lists can be empty) Every method contains a return type (can be void or nothing)

LEARNING VB .NETComparing VB .net and Java

Similarities of VB .net and Java

Both are object oriented Both have public and private methods

and attributes in a class Both use exception handling Both are event driven programming

languages

Noticeable differences between Java and VB .net

VB .net does not use semicolons VB .net does not use curly braces VB .net is not case sensitive VB .net contains both Sub Procedures and

Functions VB .net primarily contains a visual interface

for the programmer VB .net runs on multiple platforms

containing the VB .net environment Every program in this class will start off with

a form.

Primitive Data Types in Java

int float double boolean byte char Long Etc.

Primitive (elementary) Data Types in VB .Net

Integer Boolean Decimal Date Double Char String Etc.

Converting Data Types in VB .net

Functions are used to convert text (String) data to numeric data

These functions include Integer.Parse() Double.Parse() Decimal.Parse() Etc.

These functions in VB .net behave much like the parsing methods in Java.

Operators in VB .net

Math + - * / Mod (Modulus or Remainder)

Assignment =

Operators in VB .net (continued)

Comparison = (the same as assignment) < <= > >= <> (Not equal)

Boolean (uses words not symbols) And Or Not

Variable declarations in VB .net vs. Java

In java the data type is placed before the label

int num1;

In VB .net All variable declaration requires the keyword Dim

(stands for Dimension) the label is placed in front of the data type Option Explicit and Option Strict should be also turned

on at the top of every class

Dim num1 As Integer

Method Syntax in Java

public int Sum3 (int num1, int num2, int num3){

int answer;answer = num1 + num2 + num3;return answer;

} The return type is an integer The number of parameters are 3 integers The method is public

Methods in VB .net

VB .net have Three specific types of methods for classes

Each method could still be A Constructor of a class An Accessor of a class (Called Property get) A Mutator/Modifier of a class (Called Property set)

The two specific types are Sub procedures (do not return a value) Functions (return a value) Properties (act as both a mutator and/or accessor

Functions in VB .net

Functions can be both public and private Functions return a value The return type of the Function is always

at the end of the method heading (different than Java)

Only one value may be returned from a Function

Functions contain a parameter list and function label/name

Method (functions) Syntax in VB .net

Public Function Sum3(num1 As Integer, num2 As Integer, num3 As Integer) As Integer

Dim answer As Integeranswer = num1 + num2 + num3

return answerEnd Function

This Function is public This Function contains 3 parameters of type Integer This Function has a return type of an Integer

VB .NETSpecifics for developing windows

applications

Forms in VB .Net

Every form in VB .net is a class There are usually two files that are

associated with a form in vb (for this example form1 is our class name) Form1.vb which is the file containing all

methods that you write for your application

Form1.Designer.vb which holds the partial class and all the visual studio generated code

Forms in VB .net (Continued)

Forms have default attributes (properties) and methods (sub procedures and functions) which are located in the partial class file.

Properties can be set with the properties Window/Pane in the .net development environment usually located on the right hand side.

Forms in VB .net continued

Properties that can be set are Text (Title in the title bar) Background color Name of the form (Like java should match the

name of the file (class name) Size Icon (in the Title bar) Etc.

Forms can also have attributes (properties) and methods (Functions and Sub Procedures) added to them

Controls in VB .net

Items added to the form such as text boxes are called controls

Each control added to a form becomes an attribute of that form (or part of the form)

Each Control is an Object and have Attributes (properties) Methods (Functions and Sub-Procedures)

Controls can be found in the toolbox on the left hand side of the IDE.

Controls in VB .net (Continued)

All properties can be set by using the properties window for each control.

Controls in VB .net include Text Boxes Buttons Data Grids Etc.

Text Boxes

Used for entering text for a windows application

ALL Data entered in the text box is a String (like with JOptionPane)

All numeric data must be converted with the methods described earlier

The Text attribute will hold the Data entered into the text box

Events and Windows Applications

Windows is an event driven operating system (Flow of control is driven by events that occur)

Events are messages that are passed to applications and objects when something in the program occurs

Events can be a mouse click, positions of the Mouse etc.

Buttons and Event handling

By double clicking on the Button control on the form, sub program headings for handling the click event are inserted.

All code that is entered into the event handler will only execute in the program when the button is clicked.

Other event handlers for the button control include MouseHover MouseLeave Etc.

Can place code in the other event handlers by selecting the event in the upper left corner of the code view of the current Form.

Forms and event handling

another event that is handled in programs written in class is the Form load event.

The form load event handler fires every time the form loads.

All initialization can be done inside of the form load event handler.

To add a form load event handler, double click anywhere on the form and write the code needed to handle this event.

CONTROL STRUCTURES IN VB .NET

Similarities and differences between Java and VB .Net

If statements in Java

if (num1 == 4){

System.out.println(“num1 is 4”);}else

{System.out.println(“num1 isn’t 4”);

}

If Statements in VB .net

If num1 = 4 ThenMessageBox.Show(“num1 is 4”)

ElseMessageBox.Show(“num1 isn’t 4”)

End If

VB .net If statements (continued)

Again no semicolons No curly braces End If ends the if statement Single equal sign is used for comparisons

and assignments

Select Case Statements

Are a lot like switch statements in Java Unlike Java, Select Case statements will

accept the use of any data type Can be used in place of nested if statementsDim OP As String = "+" Select Case OP Case "-" Answer = Num1 - Num2 Case "+" Answer = Num1 + Num2 End Select

Loops in VB

There are many different types of loops in VB

These Loops include For Loops (counting) While Loops Do-While Loops For each Loops

For Loops are generally used for indexing lists

For each Loops are used to traverse lists of data without the use of an index

For Loop in VB

Dim Index As IntegerFor Index = 1 To 10

…… Some Code in Here ……Next The Code Block is defined between the For

statement line and the Next keyword From this example all code within the code

block will be executed ten times. Unlike Java, VB does not need to have the

statement Index++ to increment the index.

For Each Loop in VB

Dim MyList() As Integer = {1, 2, 4, 3}

For Each Item As Integer In MyList…….Some Code in Here………

Next For Each will traverse the list without the

use of an index variable Item will hold the value of each spot in

the array at each iteration of the Loop Used widely in list manipulations

While Loop in VB

Dim Counter As Integer = 0

While Counter <= 10Counter += 10

End While Will repeat the code in the code block

until Counter reaches the value of 10 The code Block is defined between the

While and End While Keywords.

Do While Loop in VB

Dim Counter As Integer = 0

DoCounter +=10Loop While Counter <= 10

The Code Block with this type of loop is located between The Do keyword and Loop While Keyword

With this example, the code block will execute 11 times

Behaves the same way as the do-while loops in Java.