Visual Basic

Visual Basic 5 is a

RAD (Rapid Applications Development) tool for creating

Windows-based applications. The product seems to be

ideally suited for creating small applications, the

client side processes of client server applications and

ActiveX controls. Applications can be generated in a

variety of formats, such as standard .EXE files, ActiveX

.EXE and .DLL files, and ActiveX Document .EXE and .DLL

formats. The product is rich in features, yet relatively

easy to learn and use.

Designing

the interface

As the name suggests the

development process in Visual Basic is largely visual.

The basic building block of a project is the form. A form

is nothing but a blank window with basic control buttons,

such as maximize and minimize buttons. The first step in

building you application is to populate the form by

placing controls on the form. The process is simple and

basically calls for selecting a control from the toolbox,

and then using the cursor to draw the control over the

surface of the form. A large number of inbuilt controls

are available which include radio buttons, check boxes,

list boxes, combo boxes, text boxes, labels, frames, and

scroll bars.

Having placed the controls

on the surface of the form, you now proceed to set the

properties of each control using the properties window.

Different controls have different sets of properties.

Some properties, such as name and size of the control,

placement and caption of the control, and the tabindex

(the order in which focus cycles through the form when

the user press the tab key) are common to all controls.

Others, such as the text in a text box, whether a text

box is multiline or the range of values in a scroll bar,

are specific to the certain controls, such as text boxes

or scroll bars.

Once you define the visual

elements of the user interface, you have to tie these

elements in with the logic of the application. This

requires linking each control on the form to what Visual

Basic calls an event procedure. The process can best be

understood by an example. Suppose you have a command

button called cmdAction on your form. Visual Basic will

automatically create a procedure called cmdAction_Click()

which will be called whenever the user clicks on this

button. The procedure will initially contain no code. To

add code to this procedure, you select the control,

invoke the code window, and locate the procedure. In a

similar manner, you can create procedures for events like

activate form, double, keydown, and the like. Event

procedures allow you to handle all the events that can

occur in connection with a particular control.

There are two ways to add

menus to your forms. The simpler method is to use the VB

Application Wizard to create a skeleton program, complete

with pull down menus and toolbars. The second is to use

the Menu Editor to create your own menus. The Menu Editor

provides a dialog box driven approach to create both menu

titles and menu commands. The Menu editor will allow you

to add spacing lines to menus, specify hot keys, and show

check marks against menu items. Each menu command is

given a name, and this name is later used to link user

selections to event procedures.

Dialog boxes are a key

component of any Windows based application and Visual

Basic provides powerful support for creating them.

Commonly used dialog boxes, such as those for File Open,

File Save, Print and Font Selection, can be created using

the Common Dialog Box control. This control allows you to

create the above dialog boxes with just a few lines of

code. For example, to create a File Open Dialog box all

you need to do is call the ShowOpen procedure associated

with the control and set the filter criteria for the type

of files to appear in the box. Visual Basic does the

rest.

Visual

Basic project structure and control

The basic unit for

developing Visual Basic applications is the project. Each

project can have different types of files associated with

it. The most common of these are form files, module

files, class files, and ActiveX controls. Each form file

contains the details of one window of your user interface

along with the procedures required by that form.

Procedures are of two types–event procedures and

general procedures. Event procedures are tied in to

specific elements of the interface. General procedures,

as the name suggests, contain procedures that are shared

across the project. General procedures stored in a form

file can be used by any event or general procedure in the

same form file.

If you want to create

truly global and shareable procedures, you have to create

what Visual Basic calls a module file. Module files have

a .BAS extension and contain general procedures that can

be used across the entire application. The process does

not end here. Visual Basic is an Object Oriented

language, and you can create classes with properties and

methods. Object classes can be shared over the entire

project. To ease the task of creating and modifying

classes, methods, and properties, Visual Basic contains

the VB Class Builder, a graphical tool for class

maintenance. Classes are stored in class files, which

have a .CLS extension. Finally, your program can contain

predefined ActiveX controls that are stored with a .OCX

extension.

Project control is

provided through the Project Explorer window. This window

displays project components in a hierarchical manner,

listing out the details of forms, modules, classes, and

the like. You can use the Project Explorer to quickly

access any component of your project and modify it.

Database

access

File handling capabilities

of classical Basic have always been something of a

disappointment. To ease the job of handling data, Visual

Basic lets you connect to databases very easily. There

are two ways to access a database from a Visual Basic

project. The first is to use the Data Control object.

This requires placing the object on the form and then

configuring the data source, so to say. The second method

is to use the Data Form Wizard. The Data Form Wizard is

simpler, but offers lesser control over the application.

Both these methods allow you to use data stored in a

variety of formats, such as xBase, Paradox, Access, or

through ODBC drivers. Visual Basic also contains a tool

called the Visual Data Manager that allows you to create

and maintain Access databases without having Access

installed in your system.

Visual

Basic Enterprise Edition

Visual Basic 5.0 is

available in a variety of editions, such as the

Enterprise Edition, the Professional Edition, the

Learning Edition, and the Control Creation Edition. The

Visual Studio suite of Windows development tools also

ships the Enterprise Edition. The Enterprise Edition is

targeted towards developers engaged in the development

and deployment of enterprise wide applications. Microsoft

has integrated several major components into the

Enterprise Edition to ease this task. These include

Microsoft SQL Server Version 6.5 Developer Edition, the

Microsoft Transaction Server, the Transact SQL debugger,

and Microsoft Visual Database Tools. In addition, the

product also includes the Microsoft Repository.

Summing

up

Visual Basic 5.0

Enterprise Edition is a balancing act between power and

ease of use. It provides developers with a fast way of

developing Windows based applications. If you’re a

developer, then give this product a hard look.