To make the application do something； you need to think in terms of events。 For example； if you have a garage with an automatic door opener； you would expect that pressing the remote control button would open the garage door when it’s closed and close the door when it’s open。 The automatic garage door manufacturer associated the event of pushing the remote control button with the action of either opening or closing the garage door。 In WindowsApplication； we’ll associate the clicking of the button with the action of showing text in the text box。 Select the button on the form in Visual Basic Express and double…click it。 The work area changes to source code； with the cursor in the Button1_Click（） function。 Add this source code to the function： TextBox1。text = 〃hello； world〃 Figure 1…7 illustrates the procedure for associating an event with an action。 Figure 1…7。 Associating the button click event with the action of adding text to the text box Note that TextBox1 is the name of the text box you added to the form。 This name is gener ated by Visual Basic Express； just as it generated a default name for the button。 You can change the default names （through each control’s Properties window）； but we’ve left the default for this example。 Adding an action to an event is very simple when following the instructions shown in Figure 1…7。 The simplicity is due to Visual Basic Express； and not because the event or action is …………………………………………………………Page 33…………………………………………………………… C H AP TE R 1 ■ R E AD Y ； ST E AD Y ； G O！ 11 simple。 Visual Basic Express makes the assumption that when you double…click a control； you want to modify the default event of the control； and as such； automatically generates the code in step 3 of Figure 1…7。 In the case of a button； the default event is the click event； that is； the event that corresponds to a user clicking the button。 The assumption of the click event being the default event for a button is logical。 Other controls have different default events。 For example； double…clicking a TextBox control will generate the code for the text…changed event。 Run the application by pressing Ctrl＋F5； and then click the button。 The text box fills with the text “hello； world。” Congratulations； you’ve just finished your first Visual Basic application。 You have associated an event with an action： the button click with the text display。 Associ ating events with actions is the basis of all Windows applications。 Adding ments to the Application Now that you have a working program； it would be good to document what it does； right there in the source code。 Then if you e back to the application in the future； you won’t be puzzled by your previous work。 In fact； you may not even be the person who maintains your code； so leaving ments in the code to help explain it is definitely good practice。 Even if you know you will be maintaining the code forever； treat your future self as a stranger。 You may be surprised how long it takes to decipher code you have written when revisited months or years later。 To add a single…line ment； use the following syntax： " A single…line ment Anything after the " on the same line is ignored by the piler and is not included in the final application。 Let’s document our Windows application： " When the user clicks the button； we display text in the text box Private Sub Button1_Click（ByVal sender As System。Object； ByVal e As System。EventArgs） Handles Button1。Click TextBox1。Text = 〃hello； world〃 End Sub The Visual Basic language is a single…line language。 This means that a statement must be part of a single line。 Let’s look at a single statement： TextBox1。Text = 〃hello； world〃 This line of code is a single statement because it is considered an assignment of one variable by another piece of source code。 You could not write the statement as follows： TextBox1。Text = 〃hello； world〃 When the statement is broken into two lines of source code； the Visual Basic piler sees it as two statements。 Since those two statements are not plete； a pilation error will result。 If you need to break a single statement over two lines； you must let the piler know by adding the line…continuation character—an underscore （_）—at the end of the continued code； as follows： TextBox1。Text = _ 〃hello； world〃 …………………………………………………………Page 34…………………………………………………………… 12 CH AP T E R 1 ■ R E A DY ； ST E A DY ； G O ！ Navigating the User Controls of the Solution When you are writing your code； your most important form of navigation is the Solution Explorer。 The Solution Explorer is the tree control that contains the references to your solutions and projects。 Consider the Solution Explorer as your developer dashboard； which you can use to fine…tune how your application is assembled and executed。 I suggest that you take a moment to click around the Solution Explorer。 Try some right clicks on various elements。 The context…sensitive click is a fast way of fine…tuning particular aspects of your solution and project。 However； when clicking； please do not click OK in any dialog box； for now； click Cancel so that any changes you may have made are not saved。 To the right of the Solution Explorer is your work area。 The work area is where you write your code or edit your user interface。 The work area will displ