© 2006 itt educational services inc. introduction to computer programming: unit 1: chapter 2: slide...
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© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 1
Unit 1
Introduction to Programming Using VB.NET
Chapter 2
Creating Applications with VB.NET
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 3
Focus on Problem Solving:Building the Hotel Directions Application
In This Section You Create Your First Visual Basic .NET Application: a Window That
Displays a Map and Road Directions to a Hotel
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
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Visualize the Application Running on the Computer and Design its User Interface
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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 placed
Label 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 7
Define the Values ofEach Control's Relevant Properties
• 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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)
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 11
Focus on Problem Solving:Responding to Events
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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 12
Augment the Hotel Application
• Now the hotelowner wants toadd an optionto view writtendirections:
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Controls to be Added
Control Type Description(Control Name)
Label Displays written directions to (lblDirections) the hotel
Button When clicked, causes the above(btnDisplayDirections) label to appear on the form
Button Stops the application(btnExit) when clicked
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 14
Direction's ApplicationControl Properties
• Label: Name: lblDirections Text: "Traveling …"
• Button Name: btnDisplayDirections Text: "Display Directions"
• Button: Name: btnExit Text: "Exit"
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 15
Method btnDisplayDirections_Click, I
Private Sub btnDisplayDirections_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs) Handles btnDisplayDirections.Click' Make the directions visiblelblDirections.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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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 visiblelblDirections.Visible = True
End Sub
Makes the control lblDirections visible:Assigns the value True to the Visible Propertyof the lblDirections control.
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 17
Syntax for Referring to theValue of a Control's Property
• ControlName• Dot• PropertyName• In this situation:
lblDirections.Visible
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 18
Syntax for an Assignment Statement
• Item receiving the value• Equal symbol• Value to be assigned• In this situation:
lblDirections.Visible = True
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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
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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
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Modifying the Text PropertyWith Code
Quite Often, You Will Need to Change a Control’s Text Property With Code
This Is Done With an Assignment Statement
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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 to1 Kilometer = 3,281 feet
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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 propertyof lblMessageThis has the effect of changingthe previously displayed value to this one
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 24
The AutoSize, BorderStyle,and TextAlign Properties
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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
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TextAlign Property for Labels
• The value of TextAlign establishes the text's justification: TopLeft TopCenter TopRight MiddleLeft MiddleCenter
– MiddleRight– BottomLeft– BottomCenter– BottomRight
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 28
Clickable Images
Controls Other Than Buttons Have Click Event Procedures
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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 namelblMessage.Text = "United States of America"
End Sub
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Using Visual Basic .NET Help
In This Section You Learn to Use the Visual Basic .NET Help System
© 2006 ITT Educational Services Inc. Introduction to Computer Programming: Unit 1: Chapter 2: Slide 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
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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
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Debugging Your Application
At Some Point, Most Applications Contain Bugs, or Errors That Prevent the
Application From Operating Properly
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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
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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