chapter 21 creating applications with visual basic.net chapter 2
TRANSCRIPT
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Chapter 2 1
Creating Applications with Visual Basic .NET
Chapter 2
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Chapter 2 2
VB Modes
Design Build and modify the project:Place, arrange, and customize controls.
Write processing scripts.
Save the project.
Run Run project as a user:Test components during development.
Demonstrate program to user during development.
Break Temporarily suspend run mode:Examine status of processing.
Determine cause of problems.
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Chapter 2 3
Example Modes
Design
Run (see error message)
Break (click Debug to see error location)
Stop (Ctrl+Break)
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Chapter 2 4
VB Structure
Create and name a project. Folder created with same name so enter name
correctly the first time! Project
Forms and other necessary components to run a program
Form Individual window interface (GUI background) Contains 1 or more controls General declarations
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Chapter 2 5
Controls Objects on a form Labels, command buttons, text boxes, etc. (each with
specific purpose and appearance)
Properties Attributes defining characteristics of control Visual appearance
Alignment Caption
Default behavior of control at run time
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Chapter 2 6
Event Procedures Signal generated at run time indicating that something
(action) has occurred to which the application must respond.
Caused by user actions, such as clicking a command button, double-clicking, or mouse over.
Based on type of control. Event Procedure: script of detailed instructions.
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Chapter 2 7
Control Planning Grid
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Chapter 2 8
Open Chapter1GrossPay project
Open project file (*.sln). See pp. 57-58 for more information.
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Chapter 2 9
Form Properties
Text (appears in title bar) Weekly Pay Calculator
StartPosition (location of format Run time) Default: WindowsDefaultLocation Change to: CenterScreen (explore other options on your own)
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Chapter 2 10
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Chapter 2 11
Controls (Review)
Refer to Table 1-2 on page 9 for a list of controls. Input from User (text box, check box, etc.) Output to User (label, image, etc.) Trigger processing (command button, menu,
etc.)
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Chapter 2 12
Control Naming Conventions
Prefix Control Example
btn Button btnExit
lbl Label lblName
txt Text txtName
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Chapter 2 13
Insert Controls
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Chapter 2 14
Form Properties Review
Text Displays text in title bar
StartPosition Controls location of form at run time
Size Controls height and width of the form
Icon Displays icon image in top left corner of title bar
BackColor Specifies the background color of the form
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Chapter 2 15
FormBorderStyle
Controls the border for the form
Value Description
Sizable (default) Enables the minimize, maximize, and close buttons.
None Displays form without a border, title bar, and sizing buttons.
Fixed3D Displays the form at specific size; can minimize and maximize, but can’t manually resize the form.
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Chapter 2 16
Properties Window (p. 60)
Categorized Alphabetized
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Chapter 2 17
Control Properties
TextAlign Location of Text value (MiddleCenter) (p. 49)
BackColor Background color (Light Yellow)
ForeColor Text color (Blue)
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Chapter 2 18
Control Size & Alignment
Click, Ctrl, Click to select. Choose Format>Align. Choose Format>Make Same Size>Both
Click + tosee details,such as specific widthand height
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Chapter 2 19
Control Sizes
Select multiple controls. Choose Format > Make Same Size >
HeightWidthBoth
Look at Width and Height property settings.
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Chapter 2 20
Equal Spacing between Controls
Select controls of similar type. Format > Vertical Spacing > Make Equal. Format > Horizontal Spacing >
Make Equal.
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Chapter 2 21
Control Properties Labels
Name: lbl prefix Text: text to display during Run Time TextAlign: Alignment of text within label control (p. 49) Font options Visible: Boolean can hold only True or False
(Discuss reasons for setting to False. See pp. 62-63.) Text Boxes
Name: txt prefix Text: empty (delete existing text) Font options
Buttons Name: btn prefix Enabled: whether can respond to user Text: text displayed within button control 3rd Button Style Property: 1-Graphical 3rd Button Picture: image selected
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Chapter 2 22
AutoSize Control Property
Specifies control’s sizing abilities False (default) maintains control’s design time size;
only partial Text value displayed if too much for size.
True enables control’s size to expand automatically to accommodate Text property value
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Chapter 2 23
BorderStyle (for Labels)
None Descriptive label
Fixed 3D Output
FixedSingle Output
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Chapter 2 24
Design After Initial Creation
Buttons:Format>Make Same Size>BothFormat>Horizontal Spacing>Make Equal
TextAlign property values(see Figure 2-13 on p. 49)
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Chapter 2 25
MS Word Font Dialog Box
What control attributes do you see? Alignment Capitalization Tab Order Access Keys
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Chapter 2 26
Focus (pp. 106-111)
Ability of a control to enable the user to interact with the program by using the keyboard. Text Box: Enter text Button: Press Enter to trigger event Label: Can’t directly receive focus; passes to
control with next TabIndex value. Only one control can have focus at a time. Control w/ focus is active control. Lose focus when go to another control.
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Chapter 2 27
Focus Method
Example: txtFirstName.Focus()
Method action: Positions insertion point in a text box to
receive input. Displays dotted borer around button.
Useful in event procedure to set focus to first text box on a form
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Chapter 2 28
TabIndex Property (pp. 107-111)
Specifies order of pressing Tab key to go from one control to another to receive focus. Set to avoid disorganized tab order due to
sequence of inserting controls. Choose View>Tab Order for visual tab order.
Starts with zero on a label (since text boxes don’t have captions). 0 for label (or check box or option button). 1 for text box relating to label Etc.
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Chapter 2 29
Access Keys (pp. 110-111)
Enables users to access controls with the keyboard.
Displays underscore for keyboard shortcut, such as File on menu bar or Exit.
Uses standard guidelines: First letter (often, not always) Other appropriate letter See other apps for examples
Requires & to left of character in Text property, such as: E&xit for Exit.
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Chapter 2 30
Access Key Considerations
Do not assign the same access key to more than 1 control on the form.
If you want to display & within the Text property, type 2 ampersand symbols: Pizza && Pasta becomes…Pizza & Pasta
Assign access key to a label that describes a text box b/c a text box can’t have access key. Assign Tab Order consecutively for label and
respective text box.
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Chapter 2 31
Accept & Cancel Buttons (p. 113)
Accept Button Triggers Click event when user presses the
Enter key. OK button
Cancel Button Triggers Click event when user presses the
Escape key. Cancel button
Form property
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Chapter 2 32
Modified Interface
0
2
4
1
3
5
Assign a high #, such as 100;VB leaves original #, which duplicatesanother TabIndex if you don’t
6 7 8
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Chapter 2 33
Event Procedures (p. 62)
Button names Description (pseudocode) Procedural Flowcharts (p. 63)
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Chapter 2 34
Pseudocode for Command Buttons
Enter Display contents of txtFirstName Display message “, you earned $”
Clear Empty contents of txtFirstName text box. Empty contents of txtHoursWorked text box. Empty contents of txtHourlyPayRate text box. Empty contents of lblGrossPay Place insertion point (set focus) in 1st box.
Exit Terminate the application.
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Chapter 2 35
Close Button Event Procedure
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Chapter 2 36
Code Window
Text-editing window to write code and remarks
Intellisense feature to automate coding (such as valid property values)
Vertical line: code region Plus sign: collapsed code for simplification Minus sign: expanded code (code you
typically create)
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Chapter 2 37
Event Procedure Explanation
Private—keyword restricting event procedure’s use to form containing its definition
Sub—abbreviation for procedure (block of code that performs a task)
KeywordsIn blue
Control name Event
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Chapter 2 38
Clear Button Event Pseudocode
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Chapter 2 39
Clear Method
ControlName.Clear () Empties the Text property value Example: txtFirstName.Clear()
LabelName.Text = “” Copies empty string to label Clear method doesn’t work on labels Example: lblGrossPay.Text = “”
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Chapter 2 40
Clear Button Event Procedure
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Chapter 2 41
Calculate Button Pseudocode
Multiplies hours worked by hourly pay rate. Displays the following string in the
lblGrossPay label:FirstName contents
“, you earned $” <literal string>
Result of calculation
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Chapter 2 42
Text Output
Output text property value from the text box to the label
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Chapter 2 43
String Literal Output
Type literal in quotation marks
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Chapter 2 44
Results of Calculation Output
Type expression.
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Chapter 2 45
Concatenate (put together)
Type & to concatenate strings for output. Press Spacebar before and after & Type _ for line continuation character and
indent continued lines of code
Note: We will learn ways to validate input and store results in variables before displaying output as we continue throughout the semester.
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Chapter 2 46
Design Guidelines
Labels close to text boxes Related options closer together Consistent space between controls Consistent space from controls to edges of
form Access keys for keyboard users Buttons
Right side with same width Bottom with same heights
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Chapter 2 47
Review
Labels Descriptive captions for input controls Output showing results
Text Boxes Input text from user
Buttons Trigger event procedure to do something with
the inputs
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Chapter 2 48
Remarks (p. 64)
Comments or explanations about code Part of program but ignored by Visual
Basic .NET Followed by an apostrophe
'Empties the text box for user input Program description
'Keith Mulbery'ISYS 1200'Assignment 1‘Gross Pay Calculating Program
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Chapter 2 49
Reasons for Remarking
Documents code for maintenance Yourself Other programmers
Saves time in understanding event procedures.
Helps others understand your logic in coding long procedures.
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Chapter 2 50
Assignment Statement
Assignment operator = Statement that copies the value on the right side
of the assignment operator to the item on the left side of the assignment operator.lblGrossPay.Text = txtFirstName.Text
Takes content of the Text property value of the txtFirstName control and copies it into the Text property of the lblGrossPay control. (p. 101)
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Chapter 2 51
Assignment Examples
Syntax: ControlName.Property Name
Example: lblDirections.Visible = True
Invalid Assignment: True = lblDirections.Visible
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Chapter 2 52
PictureBox Control (pp. 52-53)
AutoSize Adjusts automatically to fit image size; maintains proportions.
CenterImage If size is larger than image, image is centered. If image is larger than control, image displayed in center and clipped to fit.
Normal Aligns image with upper left corner of control; Clips images if too large for control size.
StretchImage Scales image to fit within the control’s size; Stretches if image is smaller than control; Shrinks if image is larger than control.
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Chapter 2 53
Locked Controls
Prevents controls from being accidentally moved at design time.
(1)Right-click empty area of form.
(2)Choose Lock Controls.
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Chapter 2 54
Types of Errors (p. 88)
Compile Error Syntax errors
Misspelled key words Incorrect use of operators Incorrect punctuation
Jagged blue underline and description displayed Run-Time Error
Not syntax Attempt to perform an operation that VB.NET can’t
carry out
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Chapter 2 55
Compile Errors
ToolTip stating compile error
Also incorrect use of .Text; should betxtState.Clear()