Unit 1 Introduction to Programming Using VB.NET Chapter 2 Creating Applications with VB.NET

1. Unit 1Introduction to Programming Using VB.NETChapter 2Creating Applications with VB.NET

2. A First Visual Basic .NET Application • Develop your first application: • Display a map and written directions to the Highlander Hotel • Use a form with labels • Use a PictureBox control • Write an event procedure

3. In This Section You Create Your First Visual Basic .NET Application: a Window That Displays a Map and Road Directions to a Hotel Focus on Problem Solving:Building the Hotel Directions Application

4. Clearly Define What the Program is To Do • Purpose: Display a map to the Highlander Hotel • Input: None • Process: Display a form • Output: Display a graphic image showing a map on the form

5. Visualize the Application Running on the Computer and Design its User Interface

6. Make a List of the Controls Needed Control Type Description(Control Name) Form A small form that will serve as (Default Name: Form1) the window onto which the other controls will be placedLabel Displays the message(Default Name: Label1) "Directions to the Highlander Hotel"PictureBox Displays the graphic image(Default Name: PictureBox1) showing the map to the hotel

7. Form Name: Form1 Text: "Directions" Label Name: Label1 Text: "Directions to the Highlander Hotel" TextAlign: MiddleCenter Font: Microsoft sans serif, bold, 18 point PictureBox Name: PictureBox1 Picture: HotelMap.jpg SizeMode: StretchImage Define the Values ofEach Control's Relevant Properties

8. Use Visual Basic .NET toCreate the Forms and Other Controls • Establish the Form • Add the Labels • Set the TextAlign Property, Font and Style • Insert a PictureBox Control • Try Running the Application

9. Project Organization on Disk • Each Solution is stored as a Visual Basic .NET Project • Within the Folder created with the project name are various files, including: • .sln contains data describing the solution • .vbproj contains data describing the project

10. Properties Window • Used to view and modify the property values of a given object • Two views of the properties: • Alphabetic (across all properties) • Categorized (groups properties by logical use)

11. An Application Responds to Events, Such As Mouse Clicks and Keyboard Input, by Executing Code Known As Event Procedures In This Section, You Write Event Procedures for the Directions Application Focus on Problem Solving:Responding to Events

12. Augment the Hotel Application • Now the hotelowner wants toadd an optionto view writtendirections:

13. Controls to be Added Control Type Description(Control Name) Label Displays written directions to (lblDirections) the hotelButton When clicked, causes the above(btnDisplayDirections) label to appear on the formButton Stops the application(btnExit) when clicked

14. Label: Name: lblDirections Text: "Traveling …" Button Name: btnDisplayDirections Text: "Display Directions" Button: Name: btnExit Text: "Exit" Direction's ApplicationControl Properties

15. Method btnDisplayDirections_Click, I Private SubbtnDisplayDirections_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles btnDisplayDirections.Click ' Make the directions visible lblDirections.Visible = True End Sub Line Continuation Mark Name of the event the procedure responds to Name of the control that owns the event procedure Marks the beginning of this event procedure

16. Method btnDisplayDirections_Click, II Private Sub btnDisplayDirections_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles btnDisplayDirections.Click ' Make the directions visible lblDirections.Visible = True End Sub Makes the control lblDirections visible: Assigns the value True to the Visible Property of the lblDirections control.

17. Syntax for Referring to theValue of a Control's Property • ControlName • Dot • PropertyName • In this situation: • lblDirections.Visible

18. Syntax for an Assignment Statement • Item receiving the value • Equal symbol • Value to be assigned • In this situation: • lblDirections.Visible = True

19. Use Visual Basic .NET toUpdate the Application • Place the label and the buttons on the form • Enter the code for the two procedures • Test the application

20. Additional Properties • Color properties: • BackColor: Sets the background color • ForeColor: Sets the foreground (e.g., text) color • Form style property value examples: • Sizable: (Default) Has normal buttons in upper right and is resizable via the edges • Fixed3D: Has a 3D look; normal buttons; is not resizable by its edges

21. Quite Often, You Will Need to Change a Control’s Text Property With Code This Is Done With an Assignment Statement Modifying the Text PropertyWith Code

22. The Text Property Can BeModified via Code, I • Suppose that a form was established with a label lblMessage that said: 1 Kilometer = ? • And on a btnfeet button click, we wanted to change the value of the text property to 1 Kilometer = 3,281 feet

23. The Text Property Can BeModified via Code, II Private Sub btnFeet_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles btnFeet.Click ' Display the conversion to feet. lblMessage.Text = "1 Kilometer = 3,281 feet" End Sub Assigns the given string to the text property of lblMessage This has the effect of changing the previously displayed value to this one

24. The Label Control’s AutoSize Property Allows a Label to Change Size Automatically to Accommodate the Amount of Text in Its Text Property The BorderStyle Property Allows You to Set a Border Around a Label Control The AutoSize, BorderStyle,and TextAlign Properties

25. AutoSize Property for Labels • AutoSize is a Boolean (True or False) Property of labels • False (the default) means that the box size will not change, depending on the amount of text assigned to it • True means that it will resize itself to fit variable amounts of text

26. BorderStyle Property for Labels • BorderStyle determines the look of the box • None (the default) means no border • FixedSingle means a border one pixel wide • Fixed3D gives it a recessed 3-dimensional look

27. TextAlign Property for Labels • The value of TextAlign establishes the text's justification: • TopLeft • TopCenter • TopRight • MiddleLeft • MiddleCenter • MiddleRight • BottomLeft • BottomCenter • BottomRight

28. Controls Other Than Buttons Have Click Event Procedures Clickable Images

29. PictureBox Control • As we saw earlier the Image Property can be set to an graphic of some sort • The image is clickable • This event can be handled by code to take whatever the appropriate action is

30. PictureBox Click Event code • When PictureBox picUSA is clicked, lblMessage is set appropriately: Private Sub picUSA_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles picUSA.Click ' Display the country name lblMessage.Text = "United States of America" End Sub

31. In This Section You Learn to Use the Visual Basic .NET Help System Using Visual Basic .NET Help

32. Dynamic Help • Dynamic Help provides help information that is relevant to the operation you are currently performing • This window occupies the same location as the Properties window • Simply select the tab at the bottom to select which you wish to view

33. Help Menu • The usual categories of Help that you are probably accustomed to in Microsoft applications • Contents… • Index… • Search… • Are available through this window also

34. At Some Point, Most Applications Contain Bugs, or Errors That Prevent the Application From Operating Properly Debugging Your Application

35. Types of Errors: Compile Errors • These are errors in the syntax (form) of your program • Visual Basic .NET will inform you of these as soon as they are found • The area of the error will be shown with a jagged blue line • A description of the error will be given in the Task List window

36. Types of Errors: Runtime Errors • These errors occur while your program is running • Visual Basic .NET will detect some of these and inform you about them • Others you must detect yourselfAlways carefully check the operation of your program to be sure that it operates as required