Applications Development

Using VB .NetNote:

The prerequisits of this course are CMP210, CMP218 or CMP219 and CMP252

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 .net

Comparing 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 CInt() CDec() CLng() Etc. (in text on page 485)

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 two 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)

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

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 .Net

Specifics for developing windows applications

Forms in VB .Net

Every form in VB .net is a class Forms have default attributes

(properties) and methods (sub procedures and functions)

Properties can be set with the properties Window in the .net development environment

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 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.

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