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Visual Basic: Introduction

CIS 115 Lecture 2. Visual Basic: Introduction. Software to Install. Visual Studio 2005 Professional Edition (Requires Windows XP Pro) MSDN Library for Visual Studio 2005 Available from MSDNAA. Visual Studio.NET.

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Visual Basic: Introduction

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  1. CIS 115 Lecture 2 Visual Basic: Introduction

  2. Software to Install • Visual Studio 2005 Professional Edition (Requires Windows XP Pro) • MSDN Library for Visual Studio 2005 Available from MSDNAA

  3. Visual Studio.NET • A platform that allows the development and deployment of desktop and web applications • Allows user choice of many .NET languages • May program in One of them • May create different parts of application in different languages • Visual Basic • C# (C Sharp) • C++ • J++ • Etc.

  4. Visual Studio.NET • Integrated Development Environment – allows the automation of many of the common programming tasks in one environment • Writing the code • Checking for Syntax (Language) errors • Compiling and Interpreting(Transferring to computer language) • Debugging (Fixing Run-time or Logic Errors) • Running the Application

  5. What is Visual Basic.Net • 4th Generation Programming Environment / Development Language • Based on BASIC language • Beginners All-Purpose Symbolic Instructional Code • Most widely used tool for developing Windows Applications • Graphical User Interface (GUI) • Menus, Buttons, Icons to help the user • Full Object-Oriented Programming Language

  6. How a VB Application is Compiled and Run

  7. Project and Solution Concepts • User creates a new project in Visual Studio • A solution and a folder are created at the same time with the same name as the project • The project belongs to the solution • Multiple projects can be included in a solution • Solution • Contains several folders that define an application’s structure • Solution files have a file suffix of .sln • Project: contains files for a part of the solution • Project file is used to create an executable application • A project file has a suffix of .vbproj • Every project has a type (Console, Windows, etc.) • Every project has an entry point: A Sub procedure named Main or a Form

  8. Project and Solution Folders/Files • Solution folder • Solution file (.sln) • Project folder • Project file (.vbproj) • Visual Basic source files (.vb) • My Project folder: contains configuration information common to all projects • The file AssemblyInfo.vb contains assembly metadata • The References folder contains references to other assemblies • The bin folder contains the executable file produced as a result of compiling the application

  9. Using Visual Studio.NET

  10. Creating an Application • Select the “Create Project” option from the “Recent Projects” box on the Start Page

  11. Default Settings

  12. Visual Basic Forms • This is a Visual BasicGUI object called a form • Forms are the windows and dialog boxes that display when a program runs. • A form is an object that contains other objects such as buttons, text boxes, and labels

  13. Visual Basic Controls • Form elements are objects called controls • This form has: • Two TextBox controls • Four Label controls • Two Button controls • The value displayed by a control is held in the text property of the control • Left button text property is Calculate Gross Pay • Buttons have methods attached to events

  14. Design Window Toolbox Solution Explorer Properties Window

  15. Creating the Application • Step 1: Add a Control to the Form – Button • Look in the Toolbox for the Button Control • Select the Button with the Mouse • Draw a Rectangle Region in the Design Window by holding the mouse button down • Release the mouse button to see your button • (Can also be added by double clicking on the button in the Toolbox)

  16. Creating the Application • Add a Second Button to the Form • Put it in the lower right corner • The project now contains • a form with 2 button • controls

  17. Control Properties • Properties • All controls have properties • Each property has a value (or values) • Determine the Look and Feel (and sometimes behavior) of a Control • Set initially through the Properties Window • Properties Set for this Application • Name • Text

  18. Name Property • The name property establishes a means for the program to refer to that control • Controls are assigned relatively meaningless names when created • Change these names to something more meaningful • Control names must start with a letter • Remaining characters may be letters, digits, or underscore

  19. Examples of Names • The label controls use the default names (Label1, etc.) • Text boxes, buttons, and the Gross Pay label play an active role in the program and have been changed Label1 txtHoursWorked Label2 txtPayRate Label3 lblGrossPay btnCalcGrossPay btnClose

  20. Control Naming Conventions • Should be meaningful • 1st 3 lowercase letters indicate the type of control • txt… for Text Boxes • lbl… for Labels • btn… for Buttons • After that, capitalize the first letter of each word • txtHoursWorked is clearer than txthoursworked • Change the name property • Set the name of button1 to btnWelcome • Set the name of button2 to btnExit

  21. Setting Control Properties • Click on the Control in the Design Window • Select the appropriate property in the Properties Window

  22. Text Property • Determines the visible text on the control • Change the text property • bntWelcome  set to “Say Welcome” • btnExit  set to “Exit” • Do not need to include the “ “ in your text field • Notice how the buttons now display the new text

  23. Event Driven Programming • The GUI environment is event-driven • An event is an action that takes place within a program • Clicking a button (a Click event) • Keying in a TextBox (a TextChanged event) • Visual Basic controls are capable of detecting many, many events • A program can respond to an event if the programmer writes an event procedure

  24. Event Procedures • An Event Procedure is a block of code that executes only when particular event occurs • Writing an Event Procedure • Create the event procedure stub • Double click on control from Design Window – for default event for that control OR • Open the Code Editor (F7 or View Menu/Code option) • Select Control & Select Event from drop down windows in Code Editor • Add the event code to the event procedure stub

  25. Open the Code Editor

  26. Select the Control for the Event Procedure • Select the btnWelcome control from the Form Controls List Box

  27. Select the Event for the Event Procedure • Select the Click event from the list of many available events • Buttons have 57 possible events they can respond to

  28. Event Procedure Stub • Beginning of Procedure is created for you • If you create stub by double clicking on control it will create a stub for the most commonly used event for that control

  29. Add the Event Code • Write the code that you want executed when the user clicks on the btnWelcome button • Type: MsgBox (“Welcome to Visual Basic”) • Must be contained within the Event Procedure Stub

  30. Writing Visual Basic Code • Not Case Sensitive • Visual Basic will “correct” case issues for you • Keywords are in Blue • Special reserved words • Comments in Green • Problems with Syntax (Language) will be underlined in blue

  31. Coding Conventions • Rules • Use spaces to separate the words and operators • Indentation and capitalization have no effect • Recommendations • Use indentation and extra spaces for alignment • Use blank lines before and after groups of related statements • Code all variable declarations at the start of the procedure • Group related declarations

  32. Comments • Usage • Type an apostrophe ( ' ) followed by the comment • The compiler ignores everything on the line after ‘ • Used for documentation/readability and to disable chosen statements during testing • Recommendations • Follow apostrophe with a star for readability ( ‘* ) • Use at beginning of program to indicate author, purpose, date, etc. • Use for groups of related statements and portions of code that are difficult to understand

  33. Code that follows recomendations '* ====================================== '* Class: CIS 115-101 '* Author: Paul Overstreet '* Purpose: Homework 1 – VB Application '* Date: 11/30/01 '* ====================================== Public Class Form1 Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventAr… '*Variable declarations Dim dOrderTotal As Decimal Dim dDiscountAmount As Decimal '*Get total from textbox dOrderTotal = txtOrderTotal.Text '*Calculate the proper discount dDiscountAmount = dOrderTotal * 0.25 ' dDiscountAmount = dOrderTotal * 0.25 End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)… ‘*Code goes here End Sub End Class

  34. Create Event Procedure for Exit Button • Create an Event Procedure for when the btnExit button is clicked • Have it display “Goodbye” in a MsgBox • Then “End” – this will terminate the program

  35. Switching to Design Window • You can switch between the Design Window and the Code Window (once opened) by clicking on the tabs at the top of the • Design and Code Windows • Form1.vb(Design) is the • design window • Form1.vb is the Code Window

  36. Running the Application • Click the Run Icon on the Standard Toolbar • Or Press F5 • This will begin the program • Display the Form/Window • Nothing will happen • Waiting on an Event

  37. Test the Events • Click on the “Say Welcome” button • The message box should display • Click on the “Exit” button • The message box should display • The application should terminate

  38. Save the Project • Make sure to save your work • SAVE ALL (not Save Form) • Visual Basic applications are • made of several files - • Often even several forms

  39. Homework • Lab Handout • Intro to VB Controls and Properties • See handout for details and due date • Questions?

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