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Week 1 – Visual Basic Tutorial 

Visual Basic 6 (VB6) - Beginners Tutorial  

Welcome to Free Visual Basic 6 (VB6) tutorial for beginners. This Visual Basic 6 ( VB6 ) tutorial helps you to learn Visual Basic 6.0 (VB6) programming in your own. Assuming you all are beginners to visual basic, each and every lesson in this tutorial is explained step by step with examples and source code.  

Visual basic is a high level programming language developed from the earlier DOS version called BASIC. Though, Visual Basic .NET is the latest technology introduced by Microsoft with tons of new features including the .NET framework and educational institues, Universities and Software Development companies have migrated to VB .NET, Visual Basic 6 is still widely learned and taught. 

Learning Visual Basic 6 is quite easier than other programming languages such as C++, C#, Java etc. This is because Visual Basic enables you to work in a graphical user interface where you can just drag and drop controls that you want to work with where you have to write bunches of code to create in C++ or C# or even in Java . If you are new to programming and want to start it in the smoothest and easiest way, then you should start it with Visual Basic. 

This Visual Basic 6 tutorial is for anyone who wants to learn to program his or her computer with Visual Basic. More importantly, this tutorial is for anyone who’s flipped through other programming resources only to be discouraged by obtuse language, jargon-ridden prose, and stuffed-shirt attitudes. The Visual Basic 6 (VB6) beginner's conversational style incorporates plain-English explanations along with short programming examples to lead the novice programmer by the hand through the techno jungle of computer programming. 

Contents 

Getting started to the lesson. Exploring ToolBar and the Properties Window .
    Visual Basic 6.0 - Properties, Methods and Events

Data Types, Modules and Operators in VB6

Variables in Visual Basic 6 (VB6)

Procedures in Visual Basic 6 (VB6)

If,Then, If...Else...Then and Select...Case Statements

VB6 Loops - Do While... Loop, While... Wend, Do...Loop While, Do Until...Loop, For...Next Loop

Exit For and Exit Do, With...End With Statements in VB6

Arrays in VB6
    Visual Basic 6 Arrays and variants
    Assigning and returning arrays
    Byte arrays
    Inserting and deleting items using arrays
    Sorting using Arrays
    Arrays of arrays

User-Defined Data Types

Constants, Data Type Conversion, Visual Basic Built-in Functions

Date and Time Functions
    Getting and Setting the Current Date and Time
    Building and Extracting Date and Time Values
    Date Arithmetic
    Format Options for Date and Time Values

Working with controls in VB6

VB6 TextBox Control
    Trapping Keyboard Activity
    Validation Routines for Numbers
    The CausesValidation Property and the Validate Event
    Auto-Tabbing Fields and Formatting Text
    Multiline TextBox Controls

CommandButton and OptionButton Controls

Label and Frame Controls

PictureBox Control and Image Control

The Timer, Line, Shape and OLE Controls

VB6 ListBox and ComboBox Controls

ScrollBar Control in VB6

Control Arrays in Visual Basic 6

DriveListBox, DirListBox, and FileListBox Controls in Visual Basic 6

CheckBox control in Visual Basic 6

Working with Forms in VB6

Working with Menus in VB6
    Accessing Menus at Run Time
    Pop-Up Menus

Multiple Document Interface in VB6

Visual Basic Functions. InputBox function

Visual Basic functions. MessageBox function

Mouse events. Positioning a control

Graphical Mouse Application. Mouse Move application in Visual Basic 6.0

Error-Handling, Debugging and File Input/Output in Visual Basic 6.0
      Error Handling Part 2

Database Access Management Using ADO - Introduction and Example Exercises
       Database Access Management Using ADO - Part 1
       Data Base Access Management Using ADO - Part 2

Dynamic Link Libraries and the Windows API in Visual Basic 6.0

Writing Code that Validates User Input

Creating ActiveX Controls

Creating Active Document

Internet Programming with IIS/Webclass and DHTML Applications

Getting Started with Visual Basic 6.0 

Visual Basic is initiated by using the Programs option > Microsoft Visual Basic 6.0 > Visual Basic 6.0. Clicking the Visual Basic icon, we can view a copyright screen enlisting the details of the license holder of the copy of Visual Basic 6.0. Then it opens in to a new screen as shown in figure 1 below, with the interface elements Such as MenuBar, ToolBar, The New Project dialog box. These elements permit the user to buid different types of Visual Basic applications.  

The Integrated Development Environment 

One of the most significant changes in Visual Basic 6.0 is the Integrated Development Environment (IDE). IDE is a term commonly used in the programming world to describe the interface and environment that we use to create our applications. It is called integrated because we can access virtually all of the development tools that we need from one screen called an interface. The IDE is also commonly referred to as the design environment, or the program. 

The Visual Basic IDE is made up of a number of components 

·        Menu Bar 

·        Tool Bar 

·        Project Explorer 

·        Properties window 

·        Form Layout Window 

·        Toolbox 

·        Form Designer 

·        Object Browser 

In previous versions of Visual Basic , the IDE was designed as a Single Document Interface (SDI). In a Single Document Interface, each window is a free-floating window that is contained within a main window and can move anywhere on the screen as long as Visual Basic is the current application. But, in Visual Basic 6.0, the IDE is in a Multiple Document Interface (MDI) format. In this format, the windows associated with the project will stay within a single container known as the parent. Code and form-based windows will stay within the main container form 

. 

Figure 1 The Visual Basic startup dialog box

Menu Bar 

This Menu Bar displays the commands that are required to build an application. The main menu items have sub menu items that can be chosen when needed. The toolbars in the menu bar provide quick access to the commonly used commands and a button in the toolbar is clicked once to carry out the action represented by it. 

Toolbox 

The Toolbox contains a set of controls that are used to place on a Form at design time thereby creating the user interface area. Additional controls can be included in the toolbox by using the Components menu item on the Project menu. A Toolbox is represented in figure 2 shown below. 

Figure 2 Toolbox window with its controls available commonly.

Project Explorer 

Docked on the right side of the screen, just under the tollbar, is the Project Explorer window. The Project Explorer as shown in in figure servres as a quick reference to the various elements of a project namely form, classes and modules. All of the object that make up the application are packed in a project. A simple project will typically contain one form, which is a window that is designed as part of a program's interface. It is possible to develop any number of forms for use in a program, although a program may consist of a single form. In addition to forms, the Project Explorer window also lists code modules and classes. 

Figure 3 Project Explorer

Properties Window 

The Properties Window is docked under the Project Explorer window. The Properties Window exposes the various characteristics of selected objects. Each and every form in an application is considered an object. Now, each object in Visual Basic has characteristics such as color and size. Other characteristics affect not just the appearance of the object but the way it behaves too. All these characteristics of an object are called its properties. Thus, a form has properties and any controls placed on it will have propeties too. All of these properties are displayed in the Properties Window. 

Object Browser 

The Object Browser allows us to browse through the various properties, events and methods that are made available to us. It is accessed by selecting Object Browser from the View menu or pressing the key F2. The left column of the Object Browser lists the objects and classes that are available in the projects that are opened and the controls that have been referenced in them. It is possible for us to scroll through the list and select the object or class that we wish to inspect. After an object is picked up from the Classes list, we can see its members (properties, methods and events) in the right column. 

A property is represented by a small icon that has a hand holding a piece of paper. Methods are denoted by little green blocks, while events are denoted by yellow lightning bolt icon. 

Object naming conversions of controls (prefix)

Form -frm
Label-lbl
TextBox-txt
CommandButton-cmd
CheckBox -chk
OptionButton -opt
ComboBox -cbo
ListBox-lst
Frame-fme
PictureBox -pic
Image-img
Shape-shp
Line -lin
HScrollBar -hsb
VScrollBar -vsb 

Visual Basic 6.0 - Properties, Methods and Events 

All the controls in the ToolBox except the Pointer are objects in Visual Basic . These objects have associated properties, methods and events.  

Real world objects are loaded with properties. For example, a flower is loaded certain color, shape and fragrance. Similarly programming objects are loaded with properties. A property is a named attribute of a programming object. Properties define the characteristics of an object such as Size, Color etc. or sometimes the way in which it behaves. For example, a TextBox accepts properties such as Enabled, Font, MultiLine, Text, Visible, Width, etc. 

·                  Enables property allows the TextBox to be enabled or disabled at run time depending on the condition set to True or False. 

·                  Font property sets a particular font in the TextBox. 

·                  MultiLine property allows the TextBox to accept and display multiple lines at run time. 

·                  Text property of the TextBox control sets a particular text in the control. 

·                  Visible property is used to hide the object at run time. 

·                  Width property sets the TextBox to the desired width at design time. 

The properties that are discussed above are design-time properties that can be set at the design tme by selecting the Properties Window. But certain properties cannot be set at desgn time. For example, the CurrentX and CurrentY properties of a Form cannot be set at the design time. 

A method is an action that can be performed on objects. For example, a cat is an object. Its properties might include long white hair, blue eyes, 3 pounds weight etc. A complete definition of cat must only encompass on its looks, but should also include a complete itemization of its activities. Therefore, a cat's methods might be move, jump, play, breath etc. 

Siimilarly in object-orinted programming , a method is a connected or built-in procedure, a block of code that can be invoked to impart some action on a particular object. A method requires an object to provide them with a context. For example, the word Move has no meaning in Visual Basic , but the statement, 

Text1.Move 700, 400 

performs a very precise action. The TextBox control has other associated methods such as Refresh, SetFocus, etc. 

·                  The Refresh method enforces a complete repaint of the control or a Form. For example, Text1.Refresh refreshes the TextBox. 

·                  The Setfocus method moves the focus on the control. For Example Text1.SetFocus sets the focus to TextBox control Text1. 

Event Driven Programming 

Visual Basic programs are built around events. Events are various things that can happen in a program. this will become clearer when studied in contrast to procedural programming . In procedural languages, an application is written is executed by checking for the program logically through the program statements, one after another. For a temporary phase, the control may be transferred to some other point in a program. While in an event driven application, the program statements are executed only when a particular event calls a specific part of the code that is assigned to the event. 

Let us consider a TextBox control and a few of its associated events to understand the concept of event driven programming. The TextBox control supports various events such as Change, Click, MouseMove and many more that will be listed in the Properties dropdown list in the code window for the TextBox control. We will look into a few of them as given below. 

·                  The code entered in the Change event fires when there is a change in the contents of the TextBox 

·                  The Click event fires when the TextBox control is clicked. 

·                  The MouseMove event fires when the mouse is moved over the TextBox 

As explained above, several events are associated with different controls and forms, some of the events being common to most of them and few being specific to each control 

Visual Basic 6 (VB6) Data Types, Modules and Operators 

Visual Basic uses building blocks such as Variables, Data Types, Procedures, Functions and Control Structures in its programming environment. This section concentrates on the programming fundamentals of Visual Basic with the blocks specified.  

Modules 

Code in Visual Basic is stored in the form of modules. The three kind of modules are Form Modules, Standard Modules and Class Modules. A simple application may contain a single Form, and the code resides in that Form module itself. As the application grows, additional Forms are added and there may be a common code to be executed in several Forms. To avoid the duplication of code, a separate module containing a procedure is created that implements the common code. This is a standard Module. 

Class module (.CLS filename extension) are the foundation of the object oriented programming in Visual Basic . New objects can be created by writing code in class modules. Each module can contain: 

Declarations: May include constant, type, variable and DLL procedure declarations. 

Procedures: A sub function, or property procedure that contain pieces of code that can be executed as a unit. 

These are the rules to follow when naming elements in VB - variables, constants, controls, procedures, and so on:  

·                  A name must begin with a letter. 

·                  May be as much as 255 characters long (but don't forget that somebody has to type the stuff!). 

·                  Must not contain a space or an embedded period or type-declaration characters used to specify a data type; these are ! # % $ & @  

·                  Must not be a reserved word (that is part of the code, like Option, for example) 

The dash, although legal, should be avoided because it may be confused with the minus sign. Instead of First-name use First_name or FirstName.