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.