Visual Basic - Chapter 2

Visual Basic - Chapter 2Mohammad Shokoohi* Adopted from An Introduction to Programming Using Visual Basic 2010, Schneider1

Chapter 2 –Visual Basic,Controls, and Events2.1 An Introduction to Visual Basic2.2 Visual Basic Controls2.3 Visual Basic Events2

2.1 An Introduction toVisual Basic 2010 Why Windows and Why Visual Basic How You Develop a Visual BasicApplication The Different Versions of Visual Basic3

Visual Basic 2010 Language used to create Windowsapplications. Provides a Graphical User Interface orGUI. The sequence of instructions executed inthe program is controlled by events.4

Sample Input Screen5

How to Develop a VisualBasic Application Design the Interface for the user. Determine which events the controls onthe window should recognize. Write the event procedures for thoseevents.6

Different Versions of VisualBasic Version 1.0 – 1991Version 2.0 – 1992Version 3.0 – 1993Version 4.0 – 1995Version 5.0 – 1997Version 6.0 – 1998Visual Basic.NET – 2002 (NOTBACKWARD COMPATIBLE WITHEARLIER VERSIONS) Visual Basic 2005 – November 2005 Visual Basic 2008 – November 2007 Visual Basic 2010 – April 20107

2.2 Visual Basic Controls Starting a New Visual Basic ProgramText Box ControlButton ControlLabel ControlList Box ControlName PropertyFonts / Auto HidePositioning and Aligning Controls8

Visual Basic Start Page9

Start a New Project10

New Project Dialog Boxselectclick on OK button11

Initial Visual Basic Screen12

Toolbox13

4 Ways to Place a Control from theToolbox onto the Form Designer Double-clickDrag and DropClick, Point, and ClickClick, Point, and Drag14

Four Controls at Design Timetext boxTo select a control, click on it. Sizing handleswill appear when a control is selected.15

Text Box Control Used for input and output When used for output, ReadOnlyproperty is set to TrueTasks buttonsizing handles16

Properties WindowPress F4 todisplay thePropertieswindow forthe selectedcontrol.categorized viewalphabetical view17

Properties ionpanesettings18

Some Often Used Properties adOnly19

Setting Properties Click on property name in left column. Enter its setting into right column bytyping or selecting from optionsdisplayed via a button or ellipses.20

Setting the ForeColor Property1. Click on ForeColor.2. Click on button atright of settings box.3. Click on Custom tabto obtain displayshown.4. Click on a color.21

Font Property1. Click on Fontin left column.2. Click onellipsis at rightof settings boxto obtaindisplay shown.3. Makeselections.22

Button Control The caption on the button should indicatethe effect of clicking on the button.Textproperty23

Add an Access Key24

Label Control Used to identify the contents of a text box. Text property specifies caption. By default, label automatically resizes toaccommodate caption on one line. When the AutoSize property is set to False,label can be resized manually. AutoSize isused primarily to obtain a multi-rowed label.25

List Box Control Initially used to display several pieces ofoutput. In Chapter 4 used to select from a list.26

The Name Property Used by the programmer to refer to a controlin code Setting for Name property near top ofProperties window Use appropriate 3-character naming prefix Use descriptive names27

Control Name PrefixesControlbuttonlabeltext boxlist tAddresslstOutput28

Renaming the Form Initial name is Form1 The Solution Explorer window lists a filenamed Form1.vb. To rename the form, change the name ofthis file to newName.vb newName should begin with prefix frm.29

Fonts Proportional width fonts, such asMicrosoft Sans Serif, use less space for"I" than for "W" Fixed-width fonts take up the sameamount of space for each character –like Courier New Fixed-width fonts are used for tables.30

Auto Hide Hides Toolbox when not in use Vertical push pin icon indicates auto hideis disabled. Click the push pin to make it horizontaland enable auto hide.push pin31

Positioning Controlsproximityline32

Aligning Bottoms of Controlssnap line33

Aligning Middles of Controlssnap line34

Tab OrderThe tab indicesdetermine the order inwhich controls receivethe focus during tabbing.The control whoseTabIndex property is setto 0 has the focus whenthe program begins.35

2.3 Visual Basic Events An Event Procedure Walkthrough Properties and Event Procedures of theForm The Header of an Event Procedure36

Event An event is an action, such as the userclicking on a button Usually, nothing happens in a VisualBasic program until the user doessomething and raises an event. What happens is determined bystatements inside the event procedure.37

Sample Statements txtBox.ForeColor Color.Red txtBox.Visible True txtBox.Text "Hello World"General Form:controlName.property setting38

Sample FormtxtFirsttxtSecondbtnRed39

Focus When you click on a text box, a cursorappears in the text box, and you can typeinto the text box. Such a text box is said to have the focus. If you click on another text box, the first textbox loses the focus and the second text boxreceives the focus.40

Examples of Events btnShow.Click txtBox.TextChanged txtBox.LeaveGeneral Form:controlName.event41

The Three Steps in Creating aVisual Basic Program1. Create the interface; that is, generate,position, and size the objects.2. Set properties; that is, configure theappearance of the objects.3. Write the code that executes whenevents occur.42

Code EditorCode EditortabFormDesigner tab43

Display Events for a Control Select the control Click on the Eventsbutton ( ) in theProperties windowevents button44

Structure of an EventProcedurePrivate Sub objectName event(.)headerHandles objectName.eventstatementsEnd Sub(.) is filled automatically with (ByVal senderAs System.Object, ByVal e AsSystem.EventArgs)45

Create an Outline for an EventProcedure Double-click on a controlor Select a control, click on the Events buttonin the Properties window, and double-clickon an event(We nearly always use the first method.)46

Sample FormtxtFirsttxtSecondbtnRedDouble-click on txtFirst to create the outlinefor the Code Editor47

Code for WalkthroughPublic Class frmDemoPrivate Sub txtFirst TextChanged(.)Handles txtFirst.TextChangedtxtFirst.ForeColor Color.BlueEnd SubEnd Class48

IntelliSenseAutomatically pops up to help the programmer.txtFirst.49

Code Editorclick tab to return to Form Designer50

Sample FormtxtFirsttxtSecondbtnRedDouble-click on btnRed to return to Code Editorand add the outline of an event procedure51

Code for WalkthroughPublic Class frmDemoPrivate Sub txtFirst TextChanged(.)Handles txtFirst.TextChangedtxtFirst.ForeColor Color.BlueEnd SubPrivate Sub btnRed Click(.)Handles btnRed.ClicktxtFirst.ForeColor Color.RedEnd SubEnd Class52

Event Procedure txtFirst.Leave Select txtFirst on the form Click on the Events button in theProperties window Double-click on Leave53

Code for WalkthroughPrivate Sub txtFirst Leave(.)Handles txtFirst.LeavetxtFirst.ForeColor Color.BlackEnd SubPrivate Sub txtFirst TextChanged(.)Handles txtFirst.TextChangedtxtFirst.ForeColor Color.BlueEnd SubPrivate Sub btnRed Click(.) Handles btnRed.ClicktxtFirst.ForeColor Color.RedEnd Sub54

Header of Event ProcedurePrivate Sub btnRed Click( ) Handles btnRed.ClickName, canbe changed.Identifies eventPrivate Sub Button Press( ) Handles btnRed.Click55

Handling Multiple EventsAn event procedure can be invoked by twoevents.Private Sub Happening(.)Handles btnRed.Click,txtSecond.LeavetxtFirst.ForeColor Color.RedEnd Sub56

Altering Properties of the Form The following won't work:frmDemo.Text "Demonstration" The form is referred to by the keyword Me.Me.Text "Demonstration"57

Open and Run an ExistingProgram Click on Open Project in the File menu.Navigate to the program’s folder.Double-click on the program’s folder to open it.Double-click on the file with extension sln.In the Solution Explorer double-click on the filewith extension vb. (The Form Designer willappear.) Press F5 to run the program.58

Visual Basic - Chapter 2 Mohammad Shokoohi * Adopted from An Introduction to Programming Using Visual Basic 2010, Schneider. 2 Chapter 2 –Visual Basic, Controls, and Events 2.1 An Introduction to Visual Basic 2.2 Visual Basic Controls 2.3 Visual Basic Events. 3 2.1 An Introduction to