Chapter 1 Introduction to Visual Basic 2010 McGraw-Hill Copyright © 2011 by The McGraw-Hill Companies, Inc. All Rights Reserved. Chapter Objectives (1 of 2) • Describe the process of visual program design and development. • Explain the term object-oriented programming. • Explain the concepts of classes, objects, properties, methods, and events. • List and describe the three steps for writing a Visual Basic project. • Describe the various files that make up a Visual Basic project. 1-2 Chapter Objectives (2 of 2) • Identify the elements in the Visual Studio environment. • Define design time, run time, and debug time. • Write, run, save, print, and modify your first Visual Basic project. • Identify syntax errors, run-time errors, and logic errors. • Use Auto Correct to correct syntax errors. • Look up Visual Basic topics in Help. 1-3 Writing Windows Applications with VB (1 of 2) • Windows Graphical User (GUI) Interface – Defines how elements look and function Text boxes Check box Radio buttons Message box Buttons Picture box Label Writing Windows Applications with VB (2 of 2) Windows are called forms. Elements are called controls and are added using a toolbox. Programming Languages—Procedural, Event Driven, and Object Oriented • Procedural—Cobol, Fortran, Basic • Event-Driven Programming(VB 6.0 and previous) • • Program specifies exact sequence of all operations. • Contain some elements of object-oriented programming, but not all Object-Oriented Programming (OOP) (VB .NET) • User controls sequence – Click event – Double Click event – Change event 1-6 The Object Model (1 of 2) In VB, you will work with objects that have properties, methods, and events. Each object is based on a class. • Objects equate to Nouns. – Forms are windows. – Controls are components contained inside a form. • Properties equate to Adjectives. – Color or size of a Form • Methods are like Verbs. – Typical methods include Close, Show and Clear 1-7 Object Model (2 of 2) • Events occur when the user takes action. – User clicks a button, User moves a form • Classes are templates used to create a new object. – Classes contain the definition of all available properties, methods, and events. – Each new object created is based on a class. • Creating three new buttons makes each button a instance of the Button class. 1-8 Object Model Analogy • Class = automobile • Properties of automobile class= make, model, color, engine, year • Object = Each individual auto is an object. – Object is also an Instance of the automobile class. • Methods = start, stop, speedup, slowdown • Events of automobile class = Arrive, Crash 1-9 Visual Studio .NET • Included in Visual Studio .NET 2008 • Visual Studio .NET Editions • Visual Basic (can also be purchased separately) • Visual C++ • C# (C sharp) • J# (J sharp) • F# (F sharp) • .NET 3.5 Framework • Express • Standard • Professional • Team System 1-10 Writing Visual Basic Projects There is a three-step process when writing a Visual Basic application—you set up the user interface, define the properties, and then create the code. •Planning • • • Design the User Interface. Plan the Properties. Plan the Basic Code; follow the language syntax rules; use pseudocode (English expression or comment describing action) then you move on to •Programming (and use the same three-step process) • • • Define the User Interface. Set the properties. Write the Basic code. 1-11 VB Application Files • • • • • • One Solution File—think of one solution file equals one project: HelloWorld.sln Solution User Options File: HelloWorld.suo Form Files: HelloForm.vb Resource File for the Form: HelloForm.resx Form Designer: HelloForm.Designer.vb Project User Options File: HelloWorld.vbproj.user Once a project is run, several more files are created by the system. The only file that is opened directly is the solution file. 1-12 Visual Studio Environment The Visual Studio environment is where you create and test your projects. In Visual Studio, it is called an •Integrated Development Environment (IDE) consisting of various tools including: • • • • • • Form Designer Editor for entering and modifying code Compiler Debugger Object Browser Help Facility 1-13 Default Environment Settings Visual Studio 2010 provides an option that allows the programmer to select the default profile for the IDE. The IDE Initial Screen The Visual Studio IDE with the Start Page open, as it first appears in Windows XP, without an open project 1-15 IDE Main Window Toolbars Document Window Form Designer Solution Explorer Window Properties Window Toolbox Help Document window Solution Explorer Properties window 1-16 Tool Box You can scroll to view more controls. To sort the tools in the toolbox: •Right-click the toolbox and select. •Sort Items Alphabetically from the context menu (shortcut menu). 1-17 Modes • • • Design Time — used when designing the user interface and writing code Run Time — used when testing and running a project Break Time — if/when receiving a run-time error or pause error "Look at the Title Bar" 1-18 Writing Your First Visual Basic Project Setting Up the Project Hello World Project 1 2 3 1-19 Planning the Project • Design the user interface. • Set up the form. – Resize the form. – Place a label and a • button control on the form using the toolbox. – Lock the Controls in place. After the user interface is designed, the next step is to set the properties. 1-20 Setting Properties • • • • Label 1 Name MessageLabel Text leave blank Button 1 Name PushButton Text Push Me Button 2 Name Text Exit ExitButton Form Name HelloForm Text Hello World by your name Setting the Form Properties • • • The default startup object is Form1 The name of the form should always be changed to adhere to naming rules The properties window shows the files properties Writing the Code • • • • • • While the project is running, the user can perform actions. Each action by the user causes an event to occur. Write code for the events you care about; the events you want to respond to with code. Code is written as event procedures. VB will ignore events for which you do not write code. VB will automatically name event procedures as the object name, an underscore(_) and the name of the event. 1-23 More on Writing the Code • When writing the code for your first project, you will use the following: • Remark Statement • Assignment Statement • Ending a Program • Editor Window 1-24 Remark Statement • • • • Also known as Comment, used for documentation; every procedure should begin with a remark statement providing explanation. Non-executable Automatically colored Green in Editor Begins with an apostrophe ( ' ) • On a separate line from executable code • At the right end of a line of executable code 'Display the Hello World message. 1-25 Assignment Statement • • • Assigns a value to a property or variable Operates from right to left — the value appearing on the right side of the equal sign is assigned to the property named on the left of the equal sign. Enclose text strings in quotation marks (" ") MessageLabel.Text=" Hello World " 1-26 Ending a Program • Methods always have parentheses. (This will help you distinguish them from Properties which never have parentheses.) • To execute a method of an object you write: Object.Method() • Current Form may be referenced as Me Me.Close( ) 1-27 Editor Window • • • Declarations Section Class list Method list 1-28 Run, Save, Modify, Print, Test, Debug, and Execute • • • • • • Run Project • Open Debug Menu, Start Debugging. • Start Debugging button on the toolbar. • Press F5, the Start Debugging command. Save Project — File Menu, Save All. Modify Project if needed. "Help is always available from the Print the Code. Help Menu or by pressing F1." Correct any Errors and Rerun. When you start executing your program, the first step is called compiling, which means that the VB statements are converted to Microsoft Intermediate Language (MSIL). Your goal is to have no errors during the compile process: a clean compile. 1-29 Print the Code • • • File Menu, Print Prints complete code listing Uses arrow symbol to denote line continuation 1-30 Finding and Fixing Errors • • • Syntax Errors • Breaks VB’s rules for punctuation, format, or spelling • Smart editor finds most syntax errors, compiler finds the rest. • The editor identifies a syntax error with a squiggly blue line and you can point to an error to pop up the error message. • You can display the Error List window and line numbers in the source code to help locate the error lines. Run-Time Errors • Statements that fail to execute, such as impossible arithmetic operations Logic Errors • Project runs, but produces incorrect results. 1-31 Naming Rules and Conventions • • • Have a set of standards and always follow them. No spaces, punctuation marks, or reserved words Use Pascal casing. • Examples –MessageLabel –ExitButton –DataEntryForm –PaymentAmountTextBox 1-32 Recommended Naming Conventions for VB Objects Object Class Example Form DataEntryForm Button ExitButton Label TotalLabel TextBox PaymentAmountTextbox Radio button BoldRadiobutton CheckBox PrintSummaryCheckBox Horizontal Scroll Bar RateHorizontalScrollBar Vertical Scroll Bar TemperatureVerticalScrollBar PictureBox LandscapePictureBox ComboBox BookListComboBox ListBox IngredientsListBox SoundPlayer IntroPageSoundPlayer Visual Studio Help Additional Info (1 of 2) • • • • • Visual Studio has an extensive Help facility. Filter MSDN help to display VB topics only. Run MSDN from hard drive, CD, or Web. You can access MSDN on the Web at http://msdn.microsoft.com The Help system display is greatly changed and improved in Visual Studio 2010. You view the Help topics in a separate window web browser from the VS IDE, so you can have both windows opened at the same time. 1-34 Visual Studio Help Additional Info (2 of 2) • The opening Help page allows you to search for a topic, or to choose from a list of topic areas such as: Welcome to Visual Studio 2010, Documentation, What’s New, Walkthroughs, etc.