an introduction to vb

8/3/2019 An Introduction to VB

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An Introduction toVisual Basic.net

By

Eng. Mohammed Badrt Mostafa

Teaching assistant-Faculty of engineering

Mechanical department-Assiut university

Mobile: 01110544110

E-mail: [email protected]

Website: mbmeducation.blogspot.com
mailto:[email protected]:[email protected]


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Section one

The interface


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Why visual basic?

.net framework technology and its merit towards

the programming languages and the freedom tochoose any language.

Ease of understanding.[simple/natural code].

Very common between developers.


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Turning to Object-oriented

programming(OOP)OOP programming enables you to develop an.exe program that can run at any PC.

The beautiful appearance of the program thanthat in the structured programming.


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The idea of OOPprogramming.OOP programming depends on that the programcontains of objects. Each object has characteristics

and properties. Our code is handling with theseobjects.

This way of programming is called the eventdriven programming. As objects contains manyevents that our code will deal with what shouldhapped when the object is exposed to that event.


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Click to edit Master text stylesSecond level Third level Fourth level Fifth level

Form[the

programinterface

]

Listof

objec

ts

Components of theprogram

Properties ofthe selected

object


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The idea of OOPprogramming-cont.

Example:

The most common event you know is the clickevent for the button object. e.g.; the program

closes when you click on the close buttonobject(internally, we coded that object to closewhen it is exposed to the click event).


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ObjectsClick to edit Master text styles

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Objects that arecommonly used in anycalculation program.

Textboxes(which receive inputs and can showoutputs in).

Labels(which is used to describe what the

object is for). Buttons(which are basic item of any program). Radio buttons(which give us options to choose

from).

List boxes(which make you choose an itemfrom a list, or to appear many items on the liste.g; the state you choose in the countysection when creating a new mail account).


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Objects that arecommonly used in any

calculation program-cont.

Combo boxes(which are used to choose among

different items. It apparently differ from the listbox in the arrow built in it e.g; the countryselection in creating mail account).

Check boxes(which enables you to choose from

different options. You can mark on many items,on the contrary, the radio button makes youchoose one option).


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Objects that arecommonly used in anycalculation program-

cont.

Group box(which make you contain many

objects for a certain shared task in a container).

Menu strip(which enhance your program bymenus).


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Section two

Programming


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Where to program[the

code editor]The visual studio provides you with a code

editor in which you type your code.

The code editor is designed to-by default-type the start and end of each code block.

The code editor automatically changes thefont you type with the type of the code yourwrite as we will see soon.


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Programming Essentials

There are basic items for any program that

any program depends on. The differencebetween one programming language toanother is the syntax that expresses each ofthem and they are:

Variable declaration. Assignments. Branching. Looping.


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1- Variable declaration

The variable is that thing that holds your data.

The variable declaration takes this form:

[scope keyword] variable name As [data type]

There are different data types:

String-Numeric-Boolean-Date


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1- Variable declaration-

cont.String data type deals with characters in a set, nomatter what these characters are: numbers, letters.

The Boolean data type is true/false data type, so, it isrepeatedly used in conditional statements.

The date data type deals with dates.

The numeric data type deals with numbers. Theseare many data types for the numeric one. Thecommonly used is Decimal.


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1- The variable

declaration-cont.The keyword that is used in the variabledeclaration statement determines the scopeof that variable, or, to what extents in the

program the variable will be valid to use, or,which part of the program will see the variableand it will be invisible for the other parts.

The most common keyword used is: Dim If we take an example to declare a variable

called essam, that hold a numeric(decimal)data, the statement will be like:

Dim essam asdecimal


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3- Branching

Branching means that you use a conditionalstatements in your code.

Two types of these statements are provided:

If statement-Select case statement

The if statement takes the form:

If(condition) then

else ifElse (when needed)


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3- Branching-cont.

The select case statement takes the form:

Select case variable name

Case() to ()

Statements

Case is =()

Statements

End select.


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4- Looping

Looping is used to do the sameoperation(execute the same code) for a certainnumber.

The best and most commonly used code forlooping is the For-Next

For counter=start to end [step()]

Statements

Next [counter]


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2- Assignments

You must remember that each object hasproperties and characteristics. The way you dealwith the object is that:you type the object name, dot, then a menu

will appear to you to choose what property ormethod of that object you want to use in yourcode.

Example: if I want to put a name(Essam) in atextbox named textbox1, then you will typethat:

textbox1.text=essam

Here, we typed the object(textbox1) name,then,


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Procedures

Each block you type your code in is a procedure. Thisprocedure as default has a declaring pre-written codefor you.

Your task is to choose the procedure that you put yourcode in. you-in more accurate and specific way-choosethe event that your code will be carried out based on it.

As explained about choosing the property text for the

textbox object properties, also, we choose the suitableevent that will generate the procedure for you in whichyou will type in your code.


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Example

In this example, you will see how to design andcode a program that multiplies two numbers.We will refer to every thing that we learned

from this presentation.


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The interface

This Program contains 8 object that are: form, threelabels, three text boxes, one button.



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Before we codeClick to edit Master text styles

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Availableeventsfor that

object

From here,we choose

the object wewant toprogram


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When we code


Theobject

name

List ofproperties

andmethod to


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The code


Automatically generated start & end

Assignment statement

assignment font is black and the start/end statement are b


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The ResultClick to edit Master text stylesSecond level Third level Fourth level Fifth level

We types 6 and 5, then we activated the clickevent procedure by clicking on the button object

which did the operation of multiplication and

showed us the result in the third textbox. You must


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Conclusion

When we want to design a program that performs acertain task, we draw its interface at first.

That interface is a number of different objects.

In your mind, the time you choose the object, youknow previously what this object is used for and thesuitable event for it.

Then you turn to the code editor. Choose the objectthat you will program, choose the suitable event. Theprocedure will appear to you requiring your code.


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Conclusion-cont.

You will start your code that includes the fourmajor items of programming we mentionedbefore restricted by their rules.

Then you run the program to test it.

Finally, you package your program.

Congratulations

an introduction to vb

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