VISUAL BASIC 6..A HAND BOOK

Visual Basic 6 ..Programming with Visual Studio 6

This article try to help beginners of 'Visual Basic' and try to deliver a complete VB6 Bible. I use simplest method to describe each section. Also include some advanced programming tutorial too.I welcome all type of suggestions from all sides to make this book outstanding. I think both teachers and students will accept this article with full mind. I also welcome those who would like co-authoring with me..

Contents

An introduction to Visual Basic Basic Features of Visual Basic IDE Features of Visual Basic Declaring and using Variables Work with variables Control structures in Visual Basic Event driven programming under Windows Platform Comments/Documentation Understanding and creating   Visual   Basic Project. Advance Visual Basic Programming   An introduction to Visual BasicMicrosoft Windows Operating is

the world’s largest using computer operating system today. Because of its user friendly features and its ability to customize it became No 1. Microsoft Visual studio is the programming solution is a power full tool for developing new packages under Windows platform.   Visual studio Provide many language under this package, Visual Basic was the simplest among them. Visual Basic as the extension of BASIC language, which was support only CUI interface (Like Command Mode, Disc Operating System).This interface has changed into a new interface called GUI. It has many advantages over CUI and allows users to develop smart applications using Text boxes, list boxes etc. Visual Basic is a powerful programming system that allows us to create application that fully makes use of facilities of Graphical User interface (GUI).  Visual Basic programming system is a window based productivity tool. It supports an event Driven

programming model rather than conventional procedure oriented model. It provides a rapid application environment, a rich set of easy to use debugging tools. How it works  In traditional applications, the application itself controls which portion of code execute and in what sequence. Execution starts with the first line of the code and follows a predefined path through the application, calling procedure as needed.   Visual Basic applications are event driven. In an event driven application, the code doesn’t follow a predefined path, it execute different code sections in response to events. Events can be triggered by the user’s actions by messages from the system or other applications or event from the application itself. The sequence of these events determines the sequence in which the code executes, thus the path through the application’s code differs each time the program runs.   With most languages, if you make a mistake in composing your code the error is caught by the compiler when you start to compile your application. You must then find and fix the errors and begin the compile cycle again, repeating the process for each error you found. In Visual Basic VB interprets your code as enter it, catching and highlighting most syntax or spelling error on the fly. It much likes an expert’s eye over your shoulder as move through the codes.  In addition to this advanced error handling techniques, Visual Basic also partially compile the code as it is entered. When you are ready to rub the program, it takes only small amount of time to finish the compilation. If the compiler find s and error, it is highlighted and you can make correction and continue running the program, in short you need not go through the compilation cycle again.

Visual Basic IDE

 Basic Features of Visual Basic  Visual Basic supports following features     Data Access Features: this allows programmers to develop database front end applications and server side components for most popular database formats including MS SQL and other

Databases.

1.      Active X Technologies: that allows programmers to use the functionality provided by other applications, such as MS Office [Word, Excel etc) and other windows applications. You can even automate applications and objects created using the professional or Enterprise editions of Visual Basic.

2.     Internet capabilities make it easy to provide access to documents and applications across internet server applications.

3.    Your finished application is a true executable (.exe) file that use a visual Basic Virtual Machine that you can freely distribute.

 IDE Features of Visual Basic

  Visual Basic posses a Integrated Development Environment [IDE] in which users can develop, run and debug their applications. Visual basic is a ‘front end’ which is used for design a screen [Called form] and also writing codes for the specific controls.

 There are different type applications we can develop with visual basic enterprise edition. These types are referred as Projects; in visual basic we create projects which include different types of modules and many forms. A good project may have many forms as it can have. Following are the major type of projects we can have in Visual Basic

 1.      Standard Exe: A standard EXE project is a typical application in which we can use the database manipulation.

2.      Active EXE, Active DLL: These types of project are available with the professional edition. Active X components are basic code building components that don’t have a visible interface and that can add special functionality to our applications.

3.      Active X Control: Using this type of project we can create our own Visual Basic controls.

4.      Active X Document EXE, Active X Document EXE:  Active X Documents are in essence Visual Basic applications that can run in the environment of container that supports hyper linking, such as internet explorer.

5.      Data Project: it is identical to the Standard EXE project type, but it automatically adds the controls that are used in accessing database to the tool box. Ti also adds the database Active X Designer to the project explorer window. Active X Designers are Visual tools for accessing and manipulating databases and generating reports.

6.      DHTML Applications:  Using this project user can be developing web pages that can be displayed in the browser’s window on the client computer.

7.      IIS Applications: Visual Basic allows user to build application that run on the web server and interact with clients over the internet with the internet information server.

8.      Add-in: We can create our own add-in for the VB IDE. Add-ins is the special commands we can add to Visual Basic menus. Add-ins helps us to extend the VB IDE.

New Project Dialog Box

 VB IDE Windows and Components

  From the New Project window we can select one type of project (We already mentioned different types of VB Projects we can create). The window have three tabs namely, New, Existing, Recent. The New Window Display the options to start New Project. The items in this window is Standard EXE, Active X EXE, Active X DLL , Active X Control, VB Application Wizard, AddIn, Active X Document EXE, Active X Document DLL. The next tab shows Options to open existing projects and the last tabs show help you to find recently worked project or the recent created programs.

   By Selecting Our First Standard EXE Project we can move to the window as shown below. This is the main IDE window of Visual Basic. You can see the form in the design section, in which you can design your application by using the items of tool box.

 Tool Box:

   Items of tool box are used to design the application interface. These items are called as Controls. Controls are basically .OCX files. You can add additional controls to tool box using Project –Components or by Pressing Ctrl + T.

The tools box contains Label, Text box, Picture Box, Image, List Box, Combo Box, Option Button, Dir List Box etc. To place a control on the form first select the control with the help of mouse and move mouse over the form. When the mouse is on the form, the curser turned into a ‘+’ and we can draw the control on the form just as drawing a

rectangle in MS Paint. The items of tools box arranged in ‘General’ Tab, you can re arrange controls in separate tabs by creating custom tabs by right click the Tool Box. Use Drag and drop to add the items to Tabs.

    The default items available on the tools box are:

1. Label: This control displays a text on the form that the user can’t edit. Labels are commonly used to identify the controls. The label box can be identified by a name by setting a name property (this can be done at design time only). The text in the label control can be change by changing the caption property.

2. Text Box: This control displays the text that the user can edit. 3. Frame: This control is used to draw boxes on the form and

group other elements. 4. Command button: The most common element of windows

interface was command button. A command button represents an action that carries out when the user click the button.

5. Check box control represents one or more choice that the user can select. One of the important property of ‘Check box’ control is ‘Value’. If the check box is marked it will be ‘1’ other wise it will be ‘0’.

6. Option button: Option Buttons/Radio Buttons appears in a group, and the user can choose only one of them. It’s ‘Value’ Property will be True if it is selected. Other wise it will be false.

7. List Box: This contains a list of options from which user can choose one more items. [In windows the Font List box is an example of the use of list box.]. The Selected item in a ListBox is given by the Text property the control meanwhile sorted property determines whether the items in the list box will be sorted or not.

8. ComboBox: This control is similar to the ListBox, but it contains a Text/ Edit field. The user can either select an item from the list or enter a new string in Edit field. The item selected from the list given by the control’s TextProperty.

9. Timer: When we need to perform tasks at regular interval we can make use of Timer. The main property of Timer Control is Interval, determines how often the timer notifies our application.

10. Picture Box: This control is used to display images and images set with Picture property. The Picture Box control also supports few functionality of generating advanced drawing.

11. Shape: This control is used to draw graphical elements such as boxes, and circles etc.

12. Image: This one is similar to Picture Box but it support less functionality and make use of less resources.

13. Line: Help use to draw a line.

14. Data: Data Control provides point add click access to data stored in database [DBMS]. It was the simplest way to access Data Base.

15. OLE: It is a window you can place on the Form to host documents from other applications. Through this control we can access the functionality of other applications within our application, if they support OLE feature.

16. File System Controls: These are set of controls which help us to add file handling capabilities to out program. They are sued together to provide an interface for accessing and exploring drives, folders and files. The file system controls are as follows

1)   Drive List Box: Used to display the drives on the system in a drop down list which the user can select.

2)  Directory List Box: Used to Display all Folders in current Drive and lets the use move up and down through the hierarchy of the folders.

3)  File List Box: This control displays a list of files in the current folder.

     These are important controls even though there are plenty of controls used in VB. Lots to we will learn more about the property, in details.

 Property Window

    Properties are the attribute of controls. Every object has properties, for example a Pen, has its Color, Metal Type,

Ink Color, Type etc. In the same manner every control in VB has many properties. By using the property fields in property box we can change appearance, text / values displayed in the controls, the manner in which it look like etc. Some properties are read only, which means that they can to change at design time only, the values of such properties can’t change using code, while others are Read and Write. You can move Property window any side of VB IDE Window, can invoke using tool bar or by Pressing F4.

 Project Explorer

 Project explorer displays Opened project and other project components such as Classes and Modules.  We can start multiple projects at the same time; you have to select the project you want to work with by selecting ‘Set as Start Up’. The project explorer has three Buttons on the Top of the window, namely View Object, View Code (F7), Toggle Folder. The first two used to move between Code Window and Form Designer. The third button helps you to change the listing style of Project Explorer. We can add Multiple Forms [SDI & MDI] and as many modules and classes we needed.

 Form Layout

 Form Layout Window is used to arrange the position of form while running the program.

 Form Designer

 The form designer is the main window in the middle of the screen, in which we can design and edit user interface. The same window displays a text editor in which we can enter and edit applications code. The form designer displays two windows, the form it self and the code window. Select the form you want to view in the project explorer, and then click one of two view buttons to see form or its code.

 VB Editor/ Code Window

 In Visual Basic, the editor is called code window, it is actually a turbo charged text editor with many productivity tool built in. we can open the code window by double clicking a form or control in the form. If we double click a form we will be taken into procedure for that control. Once the code window is open, we can go to any procedure for any object on the selected form.

 Object Browser

 Object browser allows us to browse through the Various Properties events and methods that are made available or exposed. We can access it by selecting object browser from the view menu or by pressing F2.

Declaring and using Variables

A variable is a name given to a location in Random Access Memory (RAM) where a data value is stored temporarily. The contents of the variable will lost when the program is ended, we can also alter values stored in a variable during life time of the program. Visual basic Variables can store string of Text, numbers, objects, Boolean values etc. for efficiency in sorting and using data visual basic provides a data type that store specific type of data.

Data Types and their Range

Data Types Storage Size Range of Variables

Byte 1 byte 0 to 255

Boolean 2 bytes True or False

Integer 2 bytes -32,769 to 32,767

Long 4 bytes -2,147,488,648 to 2,147,488,647

Single 4 bytes 7 digits

Double 8 bytes 14 digits

Currency 8 bytes 4 decimal place

String 10 bytes 0 to approximately 2 billion

Object 4 bytes Any object reference

Variant(With number)

16 bytes Any numeric value up to a range of Doubles.

 Syntax: - Dim <variable name> As <DtaType>

Before we make use of variables we need to declare first, in general case. The naming convention is that, name of variables

        Begin with letter        Can’t contain an embedded period or embedded type declaration character.        Must not exceed 255 characters        Must be unique with in the scope, which is the range from which the variable can         referenced a procedure, a form, so on

We can mix characters and numbers together. We make use of key words ‘DIM’ and ‘AS’ to declare a variable.

 Visual Basic has two types of variable declarations

1) Explicit declaration and

      *Place ‘Option explicit’ statement in the declaration section of a Form, Class, or      

        Modules

2) Implicit declaration.

    In the first we use a statement to define the Data Type of the variable. The statement does not assign a value to the variable but merely tell visual basic what values it can contain.

Example: - Dim name As String

Variable declared without type is called implicit declaration. These are called variants, i.e. we can store any desired value in it.

Example: - Dim Str

Str =1001

Str =”GTEC”

 Scope of Variables

Variables are not necessarily available through out the entire program. Their use can be localized to certain parts of the program only. Localizing in this variable is a part of good programming practice. The parts of program in which a variable can use is termed as ‘scope of the variable’. Global variable or Public variables can be declared in General section of the of the Form. Variable declared in the sub program or Functions are local (Private) to that Sub program or Function only.

Module Scope Variables

  Visual Basic also has module scope variables which are declared in the general section of a Code Module. Module scope variables available through out all the procedure in that Module and not in other modules/Form (if you want to do so, you must use the keyword ‘Public’ to declare them).You can create module level variables by declaring them with the Private keyword in the declaration section at the top of the Module. They can be accessed by procedures and functions in that module.

Note: -You can’t declare public variables within a procedure, only within the Declaration section of a module.

Class Module Variables

There is another important variable concerning local variable, they only exist within the Class Module. Class module has limited access to the variable, they can only access by means of the object/ variables of that class.

Static Variables

In addition to scope, variables have life time, the period of time during which they retain their value. The values in module-level and public variables are preserved for the lifetime of your application. However, local variables declared with Dim exist only while the procedure in which they are declared is executing. Usually, when a procedure is finished executing, the values of its local variables are not preserved and the memory used by the local variables are not preserve and the memory used by the local variables is declared. The next time the procedure is executed; all its local variables are reinitialized.

However, you can preserve the value of a local variable by making the variable ‘static’. By using the ‘Static’ keyword to declare one or more variables inside a procedure, exactly as you would with the ‘Dim’ statement.

*Preserve values even when the procedure, using the Static Variable is ended.

Constants

Often you will find that your code contains a constant value that reappears over and over. Or you may find that code depends on certain number that are difficult to remember numbers that, in and of them have no oblivious meaning.

In this case, you can greatly improve the readability of your code and make it easier to maintain-by using constants. A constant is a meaning full name that takes the place of a number or string that does not change. Although a constant somewhat resembles a variable, you can’t modify a constant, or assign a new value to it as you can to a variable. There are two sources for constants.

1.      Intrinsic Constants: which are provided by application and controls. Other    application like MS Office also provides a list of constants you can use with their object, method, properties. Constants are also defined in the object library for each Active X Control.2.      Symbolic or User defined Constants: By make use of the keyword ‘Const’ you          Can create constants of any type.Eg: Const pa = 1233

Data Conversion

As we know variables are used to store manipulate data we handle with the pro program we build. There are occasions that we are convert data into another Data Type. Here is a list of inbuilt function to do the job.

Function Convert An Expression to

Cbool Boolean

Cbyte Byte

Ccur Currency

Cdate Date

CDbl Double

Cint Integer

CLng Long

CSng Single

CStr String

CVar Variant

CVErr Error

 

Work with variables

Now we know different type of projects and how to variables and objects. Lets start our first variable projects.

Q) Read Principle Amount, Interest Rate, Term [Period] and calculate Interestamont         and Net amount.

1.      Start Standard EXE Project2.      Double Click the Form to reach the Code Window or press ‘F7’.3.      Then locate General Section from the Drop Down list box that appear top of the code window[Left Side]4.      Type the following code

 

Dim Amount As IntegerDim Irate As IntegerDim Term As DoubleDim IamountDim Net5.      U can use comment section to  Describe the code as follows in any part of the code window‘ This program calculate Simple Interest6.      Now we need to Read and manipulate the values. Add following codes to Click Event of Form, [Select the Click event from the Next list box from the Right side of the code window].

            Private Sub Form_Click()

Net=0    ‘ Empty Values in Variables… (Initializing Zero Values to                        

                 Variables)

Iamount=0

 

Amount=InputBox (“Enter Principle Amount”,”Variable Test”)

Irate= InputBox (“Enter Interest Rate”,”Variable Test”)

Term= InputBox (“Enter Term/Period”,”Variable Test”)

Iamout=Irate*Amount/100*Term

Net=Iamount+Amount                      

Print “ Amount”,Iamout

Print “Net amount”, Net

End Sub

7.      Now Ready to Test the project8.      Press F5 or Find Start Button from Tool Bar / Run Menu

 

*Here ‘InputBox’ is used to Input Values, it has two arguments first one is its message and second is Optional title, and i.e. u can avoid it. U can also leave the argument by inserting “ “.

*’Print’ is used to display values to Form.

 

Exercise:

1.      Read Two Numbers and do Basic Calculations (+, -, *, /)?

* Remember First think of variables and their type, you need to create.

 * If u has to display decimal points use Data Types like Double

2.      Read a number and fin Cube(x3)?

3.      Solve the equation (a+b)2?

Control structures in Visual Basic

 A control structure allows you to control the flow of your program’s execution. If left unchecked by control-flow statements, a program’s logic will flow through statement from left to right and right to bottom. While some very simple programs can be written with only this unidirectional flow, and while some flow can be controlled by using operators to regulate precedence of operations, most of the power and utility of nay programming language comes from its ability to change statement order with structures and loops.

Decision Making Statements

Decision making statements useful when we need to evaluate particular conditions and divert the execution of the program in another path/flow.

VB support two decision making statements

If……Then...…else……End if

If…. Then..…else If…..End If

Select case…..…End Select 

 

If……Then...…else……End if

 

Synax:  If (Condition) Then

  <True Block Statements>

Else

  <False Block Statements>

End if

If…. Then..…else If…..End If

Synax: 

If (Condition) Then

  <True Block Statements>

Else If <Condition> Then

  <True  Block Statements>

Else

  <False Block Statements>

End if

Select Case

 Sintax:

   Select Case(Expression)

      Case :Value1

         Statement1

      Case :Value 2 

       Statement 2

     .......................

     .......................

    Case Else

      Statement

    End Select.

    The Select Case structure compares one expression to different values. The Select Case structure tests a single expression which is evaluated once at the top of the structure. The result of the test is then compare with several values and if it matches one of the corresponding block of statement is executed. The block of Case Else statement is optional and is executed non of of the previous Case Values match the expression.

Event driven programming under Windows Platform

 As we know, Visual Basic is a vent driven programming laguage. Program responds to specific action known as Events. An Event is any action performing by using any of input devices, primarily mouse ad keyboard. When we click on specific buttons and menus, action was fired.

   For the easy handling of these events, Visual Basic uses events procedures.(Later we will discuss about different type of procedures) Visual Basic System creates event procedures. We can add code/commands that are meant to execute. 

“Envent Driven programming carries many advantages over conventional programming techniques. The first one is its ease of use and manipulates data in many ways.”

   For the best practice of event programming, we need to understand some basic events.

 Form is the container of other controls that are available in the Tool Box

Lets check out few of the important events of Form

 1.            Load….Load event occure when for loaded to the screen.

2.            Click….Event occures when user click on the form

3.            Activate…. This event occure when we make use of the form

4.            Initialize….. is triggered just before Load Event

 Comments/Documentation

Comments are the none executable sections of the programm. We can use this facility to add descriptions of code or block specific areas of the code.

We can use a ‘  (Single quote) to comment a section of the code. It can be appeared any place on the code window, no matter it is within the Event procedure or within General Section.

 For example:

 Private Sub Form1_Click ()

 ‘Display a String to Text Box Control 

 Text1.Tex = ”Welcome to Knol”

 End sub

 Understanding and creating Visual Basic Project.

   Under Visual Basic, we are creating programes as a project. Aproject has many components like Forms, Resource Files, Modules and Class Modules. These components can be seen on Project Explorer. The extension of the Visual Basic Project file is .vbp. 

Design following Program using the Text Box Control, Label and Command Button.

  Now lets add  following code in the OK button's  Click event.This will calculate the total

Private Sub OkBtn_Click()

   Text3.Text=Val(Text1.Text)*Val(Text2.Text)

End Sub

  In a Text Box Control all data you  entered is treated as string. So that we use function Val() to convert it to Integer Value. *The Text property of Text Box  return/bring the input text.

  In the Clear Button's Click Event we need yo add necessary codes to clear the Boxes.

Private Sub OkBtn_Click()'*************************************' Sample Documentation' This Section Clear the Field' ************************************

   Text1.Text=""   Text3.Text=""

  Text3.Text=""

End Sub

  Now You are ready to test your first project. Press F5  

  Remember we can programmed same thing in different ways as the programmer wish to do things.

 

 1 Build a Simple Image Viewer

 To Build a Simple Image Viewer Program we need  a Image,Drive List,Directory List,File List,Label and List Controls.  Image and Picture Controls area common in nature. Both of them have Picture property which is used to load picture to the control.In Picture control you can see that the picture is appeared in its actual size at the same time the Image control lets wrap it to the control with help of Stretch Property, Image also support some additional drawing functions.. Both the controls have a methods called LoadPicture which help us to load a specific file, all we have to do is specify the path of that picture to be shown.

Label: Label control is used to display a text. It can't be used to input value.It's main property is Caption, which display text given. 

 Drive List,Directory List,File List : These Controls work as a batch, i.e, they are meant to work together.

 Frame Control is use to group controls, so that we can move them together.We change the caption property   to  "Select a File".    Arrange these controls as shown below.  

  1.  Now Set  Stretch property of Image box to True. 2. Add a label control just above the File List control and set it's caption as "File

Type" 3. Add codes to show Directories and files  in selected file and folders.

Const Title = "Picture Viewer 1.1"                         ' Create a constant called Title. Private Sub Drive1_Change()On Error GoTo Error1:Dir1.Path = Drive1                                                      ' Display all directories in Selected Drives. Exit Sub                                                                        Error1:

MsgBox "Device Not Found"End Sub Private Sub Dir1_Change()  File1.Path = Dir1.Path                                           ' Displays  files in the Selected Folders                            End Sub Private Sub File1_Click()Image1.Picture = LoadPicture(File1.Path & "\" & File1.FileName)    Form1.Caption = Title & "/" & File1.NameEnd Sub Private Sub Form_Load()List1.AddItem "*.bmp"                                                           List1.AddItem "*.jpg"List1.AddItem "*.gif"End Sub Private Sub List1_Click()File1.Pattern = List1.TextEnd Sub

Now you are ready to test your application. You can change the icon of the form.

    

   

     

2 Creating a calculator

*Understanding control array. In Visual Basic, we can use copies of one control instance, and they act as a group, They are also called as 'Control array'. Let us build calculator.  First up all we need 9 buttons for showing the Digits (0-9).

1. Insert a button and size it and copy the control and paste, when the system prompt for Yes or No, Click on the Yes  button.

2. Next we need  4 more buttons(array of controls) for Operation handling(Such as +,-,x,/),

Insert a button and copy paste, 3 times.

1. Last, we need four more buttons (not array/copy) for “=”, ON, OFF, CE functionality and add a text box.

Now you are ready for coding.

 Declare variables first in the General section.

        Dim x, y As Integer

  Dim optr As String

1. Add following codes in the  Click Event of CommandButton 1 (code window). Hit F7 to invoke the code window.

 Private Sub Command1_Click(index As Integer)

 'These codes take necessary action to display the inserted value into the Text box. Since the Buttons are 'array, we only need a single line of code.

 Text1.Text = Text1.Text & index

End Sub

 This section store information regarding the operations required by the user and it store details as a string to variable 'optr', so that we can make use of it in the next section.

 Private Sub Command2_Click(index As Integer)

Select Case (index)

Case 0

 optr = "+"

Case 1

 optr = "-"

Case 2

optr = "*"

Case 3

optr = "/"

                                                                                                                                                                                                                            End Select

 'Store value into variables and clear the text box.

x = Val(Text1.Text)

Text1.Text = ""

End Sub

 Now we are ready for the operations.All we need is to check optr variable put necessary operation and set the out put to the text box. Add following codes to the equalto(=) button's Click Event.

Private Sub Command3_Click()

y = Val(Text1.Text)

Select Case (optr)

 Case "+"

  z = x + y

 Case "-"

  z = x - y

 Case "*"

  z = x * y

 Case "/"

 z = x / y

End Select

Text1.Text = z

End Sub

 The following code

add ON & OFF functionality to the program. All we need is to disable and enable controls, we are using. For this purpose we used the loop structure since we are using two control arrays it become simple.

 Private Sub Command4_Click()

This section ON the calculator.

 For i = 0 To Command1.UBound

Command1.Item(i).Enabled = True

Next i

For i = 0 To Command2.UBound

Command2.Item(i).Enabled = True

Next

Command3.Enabled = True

Text1.Enabled = True

End Sub

 Now you are ready to run your Calculator.

Note:

1.    You can change your Programs icon and caption as you like.

2.    Making  your project a complete stand alone application require one more step.

      Go to File->Make  and enter name for it. Now the application is a stand alone

       calculator, which means that it doesn't need VB to run the application.

  3. Create a thumb nail viewer of images.(Understanding control array )

 As we already learned control array is the copy of a control. Here we are going to experiment with the File system controls and image box as control array.

 

1. First we need to Draw Drive List box, Directory List box and file list box 

2. Set the File List Box’s Pattern property as  “*.jpg” to avoid accidental loading of files

3. Add an image box  and copy paste the box 29 time or as much you need

4. Add a list box control, in which we are going to add different picture file types/ extensions and a command button

5. Add following codes to Drive list box , Directory list boxes. 6. Set Visible property of File1 to False(Hide it)

 Private Sub Dir1_Change()

  File1.Path = Dir1.Path

 End Sub

 Private Sub Drive1_Change()

On Error GoTo tt:

Dir1.Path = Drive1

Exit Sub

tt:

MsgBox "The divice cannot acces"

End Sub

  7  .Add following codes to form’s load event.

      Private Sub Form_Load()

List1.AddItem "*.jpg"

List1.AddItem "*.bmp"

List1.AddItem "*gif"

Drive1 = "E:\"                                 ‘set initial drive

Dir1.Path = "unni"                        ‘ set initial directory   

Image1.Stretch = True                  ‘resize the picture for image box.

End Sub

8. Add following code to the list box click event, it take necessary action when you select file type from the list box and reset pattern property of the File list box.

Private Sub List1_Click()

File1.Pattern = List1.Text

End Sub

 9. Now it is time to Load thumbnail views . To do this we use the image box array. Since it is an array we can use some looping  structure.

 Add following codes to Command Button’s click Event

Private Sub Command1_Click()

Dim I, C As Integer

C = File1.ListCount

MsgBox C

If C > 29 Then

 C = 29

End If

 

It also checks the count of the files, which not be greater than that of no of image boxes. If it exceed we need to reset the value

 

For I = 0 To C

File1.ListIndex = I

Image1.Item(I) = LoadPicture(Dir1.Path & "" & "/" & File1.FileName)

Next

End Sub

10 . We also need an additional Form which we can  View picture. Add a image box to it and set stretch property value to true.On the first form ,  Double click on the image box(array) and add following code to display clicked Picture.

 Private Sub Image1_DblClick(Index As Integer)

Form2.Show

Form2.Image1.Picture = Image1.Item(Index).Picture

 End Sub

11 .Add  code to display file location  as tool tip  of the thumb view.

       Private Sub Image1_MouseMove(Index As Integer, Button As Integer, Shift As Integer,        X As Single, Y As Single)

Image1.Item(Index).ToolTipText = Dir1.Path & File1.FileName

End Sub

 Now you can test your project

Note: Remember to double click the folder

 4 . Work with Variable ... Some Basic Variable Operations

     Following program will help you to learn more about variables and help you to understand how can we control flow of the variable using ' decision making  ... statements'.This program will read Name ,Qualification and Mark secured. and also calculate  index mark according to the option user using.

1.  Create a form as follows (Use Text Boxes, Combo Box, Option buttons, Labels and check boxes) and declare following variables in the General section So as we can access them  through out all part of the form.

2. Dim indx, tot As Integer 3. In the load event of the form we should add some values to the combo box 

Private Sub Form_Load()Combo1.AddItem "100"Combo1.AddItem "1000"Combo1.AddItem "800"End Sub

1. Add following codes to the Command  Buttons Click  event.   

          'This will calculate the index markPrivate Sub Command1_Click()'NCC        - 15'NSS        - 20'ARTS       - 10'OTHERS     -  5'SPORTS     -  15' R Cross   - 5Check Box have three values 0,1,2  , 0 means unchecked,1 means checked and 2 for grayed

If Check1.Value = 1 Then  indx = 10

ElseIf Check2.Value = 1 Then  indx = 15ElseIf Check3.Value = 1 Then indx = 5ElseIf Check1.Value = 1 And Check2.Value = 1 And Check3.Value = 1 Then indx = 10 + 15 + 5End IfAs for the Check box , option too have a Value property which have only two value True/FalseIf Option1.Value = True Then indx = indx + 20ElseIf Option2.Value = True Then indx = indx + 15ElseIf Option3.Value = True Then indx = indx + 5End If

Text5.Text = indxText6.Text = indx + Val(Text3.Text)   Val() Covert a text to number

End Sub 3.  Following code will find the percentage of mark. This can be achieved through the Click event of the           Combo box. 

Private Sub Combo1_Click()Text4.Text = Val(Text3.Text) / Val(Combo1.Text) * 100End Sub

4.  Some key press event will make this program more comfortable. Let's know how can we achieve this.     Private Sub Text1_KeyPress(KeyAscii As Integer)If KeyAscii = 13 Then Text1.Text = UCase(Text1.Text) Text2.SetFocus             This will set the focus to the TextBox 2 End IfEnd Sub

Private Sub Text2_KeyPress(KeyAscii As Integer)If KeyAscii = 13 Then Text2.Text = UCase(Text2.Text)   Convert the text to Upper Case and store again it to Text Box Text3.SetFocus End IfEnd Sub' 13 is the key value for the Enter Key, so this event will be triggered when we hit the enter key.

Private Sub Text3_KeyPress(KeyAscii As Integer)If KeyAscii = 13 Then Text3.Text = LTrim(Text3.Text)     This will cut all space before the text we entered Combo1.SetFocus End IfEnd Sub

5.Creating a User defined chart using Picture box control 

     Creating a userdefined chart in VB6 will be very simpe and easy. 1.  Design a form  Picture Box  and  Labels,Text Boxes,and a command Buttons

and a Timer Control as shown bellow.Give TextBox name as TextA, TextB, TextC, TextD respectively.

2. Set Timer interval tpo 1 3.  Add following code to the Command Button’s click event.

     Private Sub Command3_Click()    Picture1.Cls

Text2.Text = 5000 - Val(TextA)

Text3.Text = 5000 - Val(TextB)

Text4.Text = 5000 - Val(TextC)

Text5.Text = 5000 - Val(TextD)

Text6.Text = 5000 - Val(TextE)

Timer1.Enabled = True

 End Sub   4. Now we need some basic calculations and need to draw lnes (as Chart Bars)

    

      Private Sub Timer1_Timer()

      We have to use some loop (what ever it is) to draw chart bars representing A B C D. After this task we       also have to stop the Timer.

 

For i = 1 To 1500

Picture1.Line (0 + i, Text2.Text)-(0 + i, Picture1.Height), vbRed

Picture1.Line (1500 + i, Text3.Text)-(1500 + i, Picture1.Height), vbGreen

Picture1.Line (3000 + i, Text4.Text)-(3000 + i, Picture1.Height), vbBlue

Picture1.Line (4500 + i, Text5.Text)-(4500 + i, Picture1.Height), vbYellow

Picture1.Line (6000 + i, Text6.Text)-(6000 + i, Picture1.Height), vbMagenta

Next i

Timer1.Enabled = False

End Sub

Advance Visual Basic Programming

  1.Create Color Picker/Shading Effect to a picture

This tutorial of vb6 explain how a programmer can create both a picture color picker and color shader.In Visual Basic ,a development environment, a coder can create picture color picker, in which user can pick the color of the picture and apply it to another .This program use some of the built in functions. 

I think this is a good source for both students and teachers as well.

   To do the work we have to SetPixel and GetPixel  built in Functions   Add these declaration as follows to the General section of the Code Module       

Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long

Private Declare Function SetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long, ByVal crColor As Long) As Long

   Secondly we have to create the Shadepicture Function , to this Please Add these code to the Module     ShadePicture     

Public Sub ShadePicture(PicSource As PictureBox, PicTarget As PictureBox, WithColor As Long, Thickness As Integer)

On Error Resume Next

Dim sRate, Col As Long

Dim X, Y As Single

Dim XMax, YMax As Single

Dim cBlue, cGreen, cRed As Double   'Determines the pixel color

Dim sBlue, sGreen, sRed As Double   'Determines the SHADING color

    'Getting the RGB values of selected color

    sBlue = Fix((WithColor / 256) / 256)

    sGreen = Fix((WithColor - ((sBlue * 256) * 256)) / 256)

    sRed = Fix(WithColor - ((sBlue * 256) * 256) - (sGreen * 256))

    'Calculate screen height & width of the image

    XMax = PicSource.Width / Screen.TwipsPerPixelX - 1

    YMax = PicSource.Height / Screen.TwipsPerPixelY - 1

    'Initialising Shading

    PicTarget.Cls

    sRate = Thickness / 10

    'Process all pixels and alter them accordingly

    For X = 0 To XMax

      For Y = 0 To YMax

        Col = GetPixel(PicSource.hdc, X, Y)

        If Not Col = 0 Then     'Because black colors are usually the borders of an 

image and never change border color.It will affect the clarity.

            'Getting the RGB values of current pixel

            cBlue = Fix((Col / 256) / 256)

            cGreen = Fix((Col - ((cBlue * 256) * 256)) / 256)

            cRed = Fix(Col - ((cBlue * 256) * 256) - (cGreen * 256))

            'Resetting the RGB values of current pixel with  the  sRate of  shading

            cRed = cRed + (sRed - cRed) * sRate

            cGreen = cGreen + (sGreen - cGreen) * sRate

            cBlue = cBlue + (sBlue - cBlue) * sRate

            If Not Col = 12632256 Then SetPixel PicTarget.hdc, X, Y, RGB(cRed, cGreen, cBlue)   'Skipping transparent col and setting the pixel

        Else

            SetPixel PicTarget.hdc, X, Y, Col

        End If

      Next Y

    PicTarget.Refresh

Next X

End Sub

   Now You are ready to Test Your First Shading Program ,By using this You can Give any color you like to the pictures you using in a VB Project

  In order to test the Program you need a Form which contain Three Picture box control[Original, Processed,ColorPallet as Picture 1] , a scroll bar, and a picture of color pallet and another as a test picture.

Then Add these Codes   

Private Sub Original_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

MsgBox Original.Point(X, Y)

End Sub

Private Sub Picture1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

    ShadePicture Original, Processed, Picture1.Point(X, Y), scrRate.Value

End Sub

Private Sub scrRate_Change()

    lbThick = scrRate.Value

End Sub

Private Sub Form_Unload(Cancel As Integer)

    Clipboard.SetText ("http://tech-guroo.blogspot.com")

    If MsgBox("Is it Satisfactory?", vbQuestion + vbYesNo, "?") = vbYes Then

        MsgBox "Please Rate my code,The site address is already copied to your clipboard", vbInformation, "ThankYou"

    Else

        MsgBox "Please give FeedBack,The site address is already copied to your clipboard", vbInformation, "Please Give FeedBack"

    End If

End Sub

   Now You are ready to test your project  You will get the followign result as you  move through colors 

 

                                      

  2. USING THE SHELL32.DLL in VB6

Shell32 is one of the many DLL files that have lots windows in built function which can be used in ur  Visual Basic program. Before we make use of these function you have to Refer the DLL by adding reference file[Brouse the shell32.dll file]. Secondly you need to create a instance of shell object which is a container of following functions.

MinimizeAllEjectPC ShutdownWindows SetTime

CascadeWindows

Explore TrayProperties FindFiles TileHorizontally TileVertically Help  

Add the following vb code to button click event

         Private Sub Command1_Click()

    Dim shll32 As New Shell

    shll32.MinimizeAll

End Sub

Private Sub Command10_Click()

Dim shll32 As New Shellshll32.EjectPC

End Sub

Private Sub Command11_Click()

    Dim shll32 As New Shell

    If MsgBox("Shut Down your PC?", vbExclamation + vbYesNo, "SHELL32") = vbYes

Then

    shll32.ShutdownWindows

    End If

End Sub

Private Sub Command12_Click()

    Dim shll32 As New Shell

    shll32.SetTime

End Sub

Private Sub Command13_Click()

    Dim shll32 As New Shell

    shll32.CascadeWindows

End Sub

Private Sub Command2_Click()

    Dim shll32 As New Shell

    shll32.Explore (Text1.Text)

End Sub

Private Sub Command3_Click()

    Dim shll32 As New Shell

    shll32.TrayProperties

End Sub

 

Private Sub Command4_Click()

Dim shll32 As New Shell

shll32.FileRun

End Sub

Private Sub Command5_Click()

Dim shll32 As New Shell

shll32.FindComputer

End Sub

Private Sub Command6_Click()

Dim shll32 As New Shell

    shll32.FindFiles

End Sub

 

Private Sub Command7_Click()

Dim shll32 As New Shell

    shll32.Help

End Sub

 

Private Sub Command8_Click()

Dim shll32 As New Shell

    shll32.TileHorizontally

End Sub

 

Private Sub Command9_Click()

Dim shll32 As New Shell

    shll32.TileVertically

End Sub