Vb Net Lecture

8/2/2019 Vb Net Lecture

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Lecture on Visual Basic .NET

I. Introduction

VB.NET is a programming language a.k.a software development

tool. Programming languages are used to create operating systems, applications

programs such a Word, Excel, Access, PowerPoint, FrontPage, Publisher, andTelecommunications programs. Everything that we do with a computer must first

be written in a programming language.

The first programming language developed is called machine language which is

written with 1 and 0. This language is often referred to a binary or digital

language. This language required the programmer to give step by step

instructions for each action in binary code. Computers only understand machine

language.

The second level programming language is called assembler language. This

language allowed the programmer to use alphabet characters such as MV (whichmeans move) that will be translated by the program into machine language. Two

methods are used to translate a programming language into machine language.

1. A compiler takes all of the source code and translates the code into

another file called the object file which is in binary format and then executes the

object file. The source file still remains. Compiled programs execute

independent of the programming language and execute much faster than

interpreted languages. Object files generally have a .exe extent. When you

compile code in vb.net it is first complied in an intermediate language (IL) andthen executed Just in Time (JIT) by the Common Language Runtime (CLR)

compiler which is distributed with the IL code when sent to a PC or an Internet

Site.

2. An interpreter take one line of the source code translates it into machine

code, executes the line, returns to the source code and gets the next line,

interprets it into machine code. This continues until all of the source code has

been translated and executed line by line from the top of the program to the

bottom. This is referred to as sequencing through the program. An interpreter

functions inside of the programming language.

The third level programming languages (Higher Level) consisted of

languages that were closer to natural languages. Cobol, RPGII, Qbasic,

Pascal, C, C+++, Fortran are examples of third level languages. These

languages allow you to use English words such as print, input, and read to write

program code.

The fourth level languages are the visual languages such as Visual Basic,

VB.NET and Visual C+++. These are also called Object Oriented Programming




languages because they attached code to objects (icons/visual pictures).

Windows 98 was written using OOP.

The fifth level languages are the voice actuated languages. Windows Office

XP comes bundled with voice actuation and writing pad actuation.

II. Visual Basic.NET Object-Oriented programming

Language A.K.A as OOP.

Visual Basic .NET combines a graphical interface called the Integrated

Development Environment (IDE) and programming code to make program

development as rapid as possible. The IDE contains tools for creating, testing

and running computer programs.

The core of the .net environment is the IDE known as Visual Studio.Net (VSN).VSN includes visual basic.net among several other programming languages such

as C#.net and C+++.net. Microsoft also sells the IDE to third party vendors who

use it for their own programming languages. There are three way of writing code

in the IDE.

1. Console mode applications in which the code is run from the XP command

Prompt. This is the same mode as earlier versions of Basic, BasicA, and

Qbasic. There is no graphic user interface.

2. Windows-based mode applications in which code is written and run in

windows graphic interface on the desktop. When writing code in the window

mode objects are created which are event (action) driven and execute code

attached to the graphic object.(OOP). The user interface in the windows mode is

a form in which objects are placed and code attached in the background.

3. Web-based mode applications has a web user interface and runs on a web

server that can be accessed using a computers internet browser.

Code can be written to execute in the Command Prompt environment, Windows

environment, and Web Server environment using the IDE.

An object is anything that can bee seen, touched, or used; whenever you go to

the start button in window you are going to an object.

Attributes are the characteristics that describe the object. When you tell

someone that you have a Pentium 4 computer that runs at 4 GigaHz, a DVD

drive and 1 GigByte of Memory you are describing some of the attributes of your

computer.




An objects behavior also referred to as methods are the operations (actions)

that the object is capable of performing. Your computer can save digital files to a

hard drive, transmit and received data over the internet, be used for word

processing, etc.

A class is a structure, design used to build an object and includes(encapsulates) the attributes and behaviors of the object. Your computer would

be a class that has the above attributes and behaviors. A class is not an object

until it has been built. Your computer did not become an object until an

instances (the building of the computer, the use of the class in the program) of

the class occurs.

Abstraction refers to the hiding of the internal detail of an object from the user.

This prevents the user from changing the object when they should not be

messing with it. Attributes that are not hidden are said to be exposed to the

user. You only want to expose the behaviors and attributes that are necessaryfor the user to complete their job and hide all of the rest of them.

Once you create a class you can create another class from it called a derived

class. The derived class inherits (inheritance) the attributes and behavior from

the base class (the class from which it was built). When you buy a new

computer the salesman will show a base machine, and then will show you one

with a DVD, Joy Stick, Large Monitor, Wireless Keyboard, etc. The computer

with all the bells and whistles is derived from the base class and inherits all of its

attributes and behaviors and has some of its own.

Polymorphism is the oop feature that allows the same instruction to be carried

out differently depending on the object. You open a file, open a form, open a

report, etc.

An event (action) is something that occurs to an object. When you left click the

start button (object) on the window desktop a pop up window comes up that

allows you to access the programs. The left click was an event that executed

code that was attached to the object. If you right click the start button the

response will be a different pop up menu. The right click action executes

different code on the object. One object can have many different events

associated with it. Visual Basic. Net is an event driven OOP language.

Visual Basic .Net is a graphical programming language that let you build a

complete application without writing any source code. The functionality of the

application will be very limited without writing code.

Writing Source code attached to objects.




All computer languages operate within the Structured Theorem parameters

which allow the solving of programming problems with:

1. Sequencing in which source code is executed line by line from top to

bottom. All computers execute source code starting at the top of the program

and continue to the bottom (end) of the program code.

2. Selection in which a branch of code is executed based on a true or false

condition. The control structures used with selection are if, then, endif for single

selection, if, then, else, endif for two way selection statement, and a if, then,

elseif, then, else enidif for multiple selection.

IF condition1 THEN

[statementblock-1]

[ELSEIF condition2 THEN[statementblock-2]]...

[ELSE

[statementblock-n]]

END IF

If age < 30 then

Print "You are less than 30 yrs old"

ElseIf age <40 then

print "You are less than 40 yrs old"Else

Print "You are older than 40"

End If

3. Iteration (looping, repetition) in which a branch of code is executed over

and over while a condition is true. The control structures are Do-While-Loop, Do-

Loop-Until, and For-Next for iteration statements.

DO [{WHILE | UNTIL} condition]

[statementblock]

LOOP

or

DO

[statementblock]

LOOP [{WHILE | UNTIL} condition]

FOR counter = start TO end [STEP increment]

[statementblock]

NEXT [counter [,counter]...]

4. Select Case allows selection of a branch of code based on a pre-selected

condition being true. My friend Brian Marshall considers that the Select Case is a

selection statement and that Structured Theorem only has three elements. The

control structure for select case is




SELECT CASE testexpression

CASE expressionlist1

[statementblock-1]

[CASE expressionlist2

[statementblock-2]]...

[CASE ELSE[statementblock-n]]

END SELECT

In summary all computer programming languages solve problems using

sequencing, selection; iteration and case select control structures. We will be

working with the above control structures when we write code behind the objects.

Additionally data used during program execution is obtained through three

primary ways.

1. Data is stored within the program. VB.Net does this by using a dimensioned

array with a list. For example:

Dim strMonth() as String =

{"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"}

will store in memory in elements 0 to 11 for the strMonth variable the above data.

This is called an initialization list which will automatically set the upper bounds of

the array equal to the length of the list.

2. Data is input from the keyboard or other device. Text boxes are the fields

place on dialog boxes and in other windows that allow the user to enter a value.

The characters entered into a text box needs to be converted into a numeric

value before mathematical operations can be performed. The Val function takes

number that are in text format and returns a numeric value that can be used in

calculations.

lblTotal.Text=Val(txtPrice.Text) In this example the data contained in the

txtPrice.text box will be converted into a number and assigned to the lblTotal.text

box.

3. Data is written to or input from a disk storage device.

III. Creating a project using Microsoft Visual Studio

.NET

Click on new project:




Definitions

A Graphical User Interface (GUI) is the visual part of a program containing

forms and controls.

A control is a visual object on the screen that helps the program to communicate

with the user by accepting input or displaying output.

Multi-tasking is the process of doing more than one thing at a time.

A front-end program is a client application that connects to a database or other

server program.

A back-end program is a server program that accepts connections from client

applications.

A multi-processing systems are computers with more than one processor that

are capable of handling more data-processing tasks than computers with just a

single processor.




Lesson 1 – Things to remember in Visual Basic .NET

1. Microsoft Visual Basic.NET is a software development tool that allows

you to create Windows programs. VB.net is a part of Visual Studio.Net

2. VB.NET project is made up of several files.a). VBPROJ extension - holds data about a project.

b). SLN extension - information about a solution is stored in this file.

c). The solution explorer allows you to see and open the forms and

other files that make up a project.

3. The properties window lets you view the characteristics or properties of

the objects and make changes to those properties.

4. The toolbox holds the tools that allow you to add objects to a form.

5. To run a program, click the start button on the Standard toolbar.

6. The integrated Development Environment

Lesson 2 – To start in Visual Basic .NET

1. The Windows application project type allows you to create a program

from scratch.

2. All windows applications begin with a blank form and must have at least

one form that becomes the window when the program is run.

3. All other objects are contained within the form(s).

4. By default a window created in VB.Net can be moved, resized,

maximized minimized, and closed.

5. Properties are the characteristics of an object and can be changed in theproperties window.

a). The text property controls what the user sees in the title bar of a

form and in other objects.

b). The Name property allows the developer to refer to objects using

a meaningful name in programming code.

6. Controls are the objects that make up the user interface.

7. A button is a standard pushbutton control the commonly appears in

dialog boxes. They can be moved, resize and deleted like other objects.

8. Focus refers to the active status of an object in the window. Only oneobject can have the focus at a time. Focus is controlled by the tab order.

9. BackColor property controls the background color of a form.

10.Location property can be used to accurately position objects by Pixels.




Lesson 3

1. Windows is an event/action-driven environment which requires the user to

take an action to control the work being done.

2. Event procedures must be written for event you wish to handle, click, or

double click, or right click.

3. To access the code window double click the object. (an event)

4. VB.NET code is written in sections called sub routines.

5. VB.NET has intelliSense feature to help format our program code. It

offers what must follow the original code.

6. The end statement ends a program.

7. PictureBox tool allows you to add a picturebox control to a form. Use thename property.

8. The SizeMode property set to StretchImage cause a picture to resize to fit

the dimensions of the Picture Box control. AutoSize cause a PictureBox

control to resize to fit the picture.

9. Visible set to False will hide object. Visible set to True will display object.

10.VB.NET code is often used for setting properties of an object which allows

the change of properties while the program is running.

11.To change properties to from code you send a message to the object

which uses a method to change the property.

12.A button with a & in front of a letter in the Text property cause that letter tobecome an access key. A button named in the form's AcceptButton

property will be activated when he user presses the enter key. The

CancelButton property will be activated by the Esc key.

Lesson 4 – Simple Math in VB .NET

1. Operators perform specific operations.

a). + add values

b). - subtracts the value to the right of the operator from the value to

the left of the operator. Also can be used to perform unarynegation.

c). = assigns the result of the expression on the right of the operator tot

he item to the left of the operator.

d). * (asterisk) is used to multiply - e.g. 5*2=10

e). / (forward slash) is used for division - e.g. 5/2=2.5

f). \ (black slash) is used for integer division - e.g. 5/2=2

g). mod is used for module division which returns the remainder

- e.g. 5 mod 2 = 1




2. Values keyed directly into code are called hard-coded values or literals

(constants)

3. Text boxes allow the user to enter a value.

4. The VAL() functions is used to convert text numbers in a text box to

numeric values.

5. The _ (underscore) is called the line-continuation character.6. An ' (apostrophe) is used for a comment line that is not executable.

7. The FIX() functions removes the fractional portion of a number by

truncating.

Mathematical Order of precedence for evaluating expressions/formulas.

Mathematical Operator Use

^ - exponential 3^3 = 27

* - multiply 3*3 = 9

/ - divide 5/2=2.5

\ - integer division 5\2 = 2

mod - modular division 5 mod 2 = 1

+ - add 5 +2 = 7

- - subtract 5 - 2=3

( ) parenthesis do what is inside first

Lesson 5 -

1. The exponential operator (^) raises a number to a power.

2. The rules that dictate the order that math operators are applied in a

formula are called the order of operations.

3. Parentheses can be used to override the order of operations.

4. The Visible property can be used to hide a label until you are ready for the

user to see it.

5. The apostrophe is used to add comments to VB.NET code. Internal

Documentation.

6. Run-time errors (exceptions) occur while the program is running.7. Try/Catch/EndTry is used for error trapping.

8. Exit Sub is used to exit an error.

9. MsgBox function pops up a dialog box, delivering a message to the user.

10. When a error can not be completely handled, send message to user and

use exit sub to end the event procedure before the error can cause

additional problems.




Lesson 6 -

1. Data can be in the form of numbers, text, dates, pictures, and even sound.

2. VB.NET supports a set of data types. Whole numbers, floating-point numbers

(decimals), text, dates, and more.

Data Type Range

Byte 0 - 255

Short -32,768 to 32,767

Integer -2,147,483,648 to 2,147,483,647

Long-9,223,372,036,854,775,808 to

9,223,372,036,854,775,807

Decimal Types

Single -3.402823E+38 to 3.402823E+38

Double -1.79769313486232E+308 to 1.79769313486232E+308

Decimal-922,337,203,685,477.5808 to

922,337,203,685,477.5807

Other Types

String 1 to 65,000 characters

Date Jan 1,0001 to dec 31, 9999

Boolean True or False

Object Varies

3. Data stored in memory locations are called variables.

4. AutoSize property will adjust the size of a control to fit its contents.

5. The Dim statement is used to declare variables.

6. Variable names

a. Must begin with a letter.

b. After the first character letters, numbers and Underscore(_) are allowed.

c. No spaces in name

d. <=255 characters in name

e. Variable name prefixes.

Prefix Data Type Example

byt Byte bytCount

srt Short srtIndex

int Integer IntPeople




lng Long lngInches

sng Single sngWeight

dbl Double dblMass

dec Decimal decSalary

str String strName

dte Date dteAnniversary

bin Bollean binSold

obj Object objValue

7. Scope indicates what procedures have access to a variable. Local, Form-

level, or global.

a. Local is declared within an event procedure.

b. Form-level is declared in the declarations section of a forms code window.

c. Global is declared in a code modules declarations sections.

d. general rule is to declare variables locally.

8. Declarations section of a form's code window allows you to declare form-level

variables.

9. Object data type can hold may different kinds of data, but is less efficient than

specific data types.

Lesson 7

1. Strings hold text or alphanumeric data

2. String is a data type3. Text in a string variable must be placed in quote marks

4. The assignment operator (=) can be used to assign text fro a text box to a

string variable or from a string variable to another string variable.

5. Concatenation is the process of appending one string to the end of another

using the &.

6. Single, double, and Decimal data types hold decimal data.

a. decimal data type is specifically designed for handling dollars and cents to 4

decimal places.

7. Format() function can be used to format decimal values, phone numbers, and

more.

Symbol Description

0Cause a digit to appear in the space, if the data has no value a 0

appears

#Cause a digit to appear in the space, in the data has no value

nothing appears

. Used to specify where you want the decimal point to appear in the




format

, commas will appear in the output

%Causes a number to be multiplied by 100 and a % sign at the end of

the number

8. The Enabled property is used to make a control inactive or active.

9. The SelectionStart and SelectionLength properties and the Len() function can

be used together to highlight the text in a text box.

Lesson 8

1. Comparisons are made using conditional operators

Conditional

OperatorsDescription

= Equal to

> Greater than

< less than

>= Greater than or equal to

<= Less than or equeal to

<> Not

2. Decisions are reached by making comparisons.

3. Conditional operators compare values and return either true or false.

4. A boolean variable can be used to store the results of an expressions that

include conditional operators.

5. Selection (decision statements) in which a branch of code is executed based

on a true or false condition. The structures used are if, then, end if for single

selection, if, then, else, end if for two way selection statement, and a if, then,

elseif, then, else, end if for multiple selection. The if statement is the most

common way to make a decision in a program.

6. Flowcharts allow programmer to plan and document program code using

symbols connected by lines.

decision

processing

input output




7. Check boxes are used for Yes/No, or turn option on/off. Can be set to checked

or unchecked in properties.

8. Logical operators can be used to combine several comparisons into one

statement.

AND

A B C Result

True True True True

False True True False

False False True False

False False False False

OR

A B C ResultTrue True True True

False True True True

False False True True


XOR

A B C Result

True True True False

False True True True

False False True True





Not

A Result

True False

False True

Operator Precedence used in evaluating expressions

High ^ Arithmetic

Unary + or -

* / \ mod

+ -<, >, <=, >=, =, <> Relational

NOT Logical

AND

Low OR and XOR

Lesson 9

1. If statements can be nested inside of each other. Indent the nested if so you

can keep them straight. Each If must have an Endif.2. Radio (Option) buttons appear in groups. Only one can be active in the group.

3. Create a GroupBox to contain the radio buttons. The controls in a Groupbox

are treated as one unit.

4. The text property of a groupbox control specifies the text that appears at the

top of the groupbox.

5. To place a radio button in a group box, click and drag to groupbox. Do not

double click.

6. The text property of a radio button specifies the text that appears on the label

attached tot he radio button.

7. Coding radio buttons involves using form-level variables that carry values that

reflect the selected radio.

8. A form's Load event procedure is executed each time the from is loaded and

opened by the program.

9. The Select Case statement allows you to make multi-way selections.

a. The case can test a range or use conditional operators. Only selects the

true.

b. When using conditional operators the Is must be used. Case is >5.




c. Case else is applied in no other case is true.

Lesson 10

1. Iteration is another word for looping. Iteration allows us to repeat code overand over while a condition is true/false or until a condition becomes true/false.

a.Do while test the condition at the beginning of the loop. The loop may or may

not execute once.

b. Do until test the condition at the end of the loop. The loop will always loop

once.

c. Do While age >5

Loop

d. Do

Loop until age >5

2. InputBox function creates a window that prompts the user for input.a. text for the prompt

b. title for the window's title bar

c. optional default text for the text box.

d. InputBox(" ", " ", " ")

3. Sometimes long event procedures can make a program unresponsive to other

events.

4. An endless loop is a loop in which the condition which stops the loop is never

met.

a. Ctrl+Alt+Break will pause an endless loop.

5. The Application.DoEvents subroutine allows the program to process other

events while an event procedure is executing.

6. Loops can be nested in the same way that If statements are nested.

Lesson 11

1. ListBox control is used for displaying list of information.

a. Items.add method adds items to a listbox control

b. Items.Clear method remove entries in a listbox control.

2. For, Next loop is used for executing code a specific number of times.

a. Statements between the for and the next are executed.

b. Always involve a counter variable.c. Step key word can be used to change increment value.

d. Step key word can be used to count backwards.

e. can be nested

f. indenting code with nested for next is helpful

3. Font property is used to change the font, style, and size of a label




Lesson 12

1. Arrays use an index or subscript to access different variable with the same

name.

2. All elements of the array are of the same data type.

3. Arrays are declared by specifying the upper bound of the array.

a. Dim intMonth(11) as Integer - reserves 12 elements -0 to 11 lowerbound=04. Arrays can be declared using initialization lists that set the starting values of

the array.

a. The upper bound limit is calculated by the system based on the number of

items in the list.

b. Dim StrMonth() as

String={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"}

c. Creates a 12 element array - Jan in 0, Dec in 11.

5. Individual element in an array are read or changed by using an index value in

() to identify the element to use.

6. The GetLowerBound and GetUpperBound methods can be used to check thatan index value is in the allowable range.

7. The length method of an array returns the number of elements in an array.

8. Arrays can be processed sequentially using a loop.

a. a loop can be used to apply the same process to each element in an array.

b. Set each element in an array to a specific value

c. can be used to prompt for input for each element in an array and set its

value

d. can be searched by using an if statement in a loop that compares each

element of the array with a specific value.

9. Parallel arrays are any number of arrays, which may be of different data types,

that hold information in corresponding elements.

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