1. Chapter 2: Designing Applications
Programming with Microsoft Visual Basic .NET, Second Edition

2. Planning an Object-Oriented (OO) Application in Visual Basic
Planning an Object-Oriented (OO) Application in Visual Basic .NET Lesson A Objectives
Plan an OO application in Visual Basic .NET
Complete a TOE (Task, Object, Event) chart
Follow the Windows standards regarding the layout and labeling of controls
Programming with Microsoft Visual Basic .NET, Second Edition

3. Solving the Problem Using a Procedure-Oriented Approach
Emphasis of a program is on how to accomplish a task
A flowchart uses standardized symbols to show the steps needed to solve a problem
Pseudocode uses English phrases to describe the required steps
User has little, if any, control
Programming with Microsoft Visual Basic .NET, Second Edition

4. Solving the Problem Using an Object-Oriented (OO) Approach
Emphasis of a program is on the objects included in the interface and the events that occur on those objects
You will use a TOE (Task, Object, Event) chart to assist you in planning your object-oriented programs
User has a lot of control
Programming with Microsoft Visual Basic .NET, Second Edition

5. Solving the Problem Using an Object-Oriented (OO) Approach (continued)
Sample TOE chart
Programming with Microsoft Visual Basic .NET, Second Edition

6. Creating an OO Application
Figure 2-6: Processes used by a builder and a programmer
Programming with Microsoft Visual Basic .NET, Second Edition

7. Planning an OO Application
Actively involve the user in the planning phase
Planning an OO application requires the following steps:
Identify the tasks the application needs to perform
Identify the objects to which you will assign those tasks
Identify the events required to trigger an object into performing its assigned tasks
Draw a sketch of the user interface
Programming with Microsoft Visual Basic .NET, Second Edition

8. Identifying the Application’s Tasks
What information, if any, will the application need to display on the screen and/or print on the printer?
What information, if any, will the user need to enter into the user interface to display and/or print the desired information?
What information, if any, will the application need to calculate to display and/or print the desired information?
Programming with Microsoft Visual Basic .NET, Second Edition

9. Identifying the Application’s Tasks (continued)
How will the user end the application?
Will previous information need to be cleared from the screen before new information is entered?
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10. Identifying the Objects
After completing the Task column of the TOE chart, you then assign each task to an object in the user interface
You use a label control to display information that you do not want the user to change
You use a button control to perform an action immediately after it is clicked by the user
You use a text box to give the user an area in which to enter data
Programming with Microsoft Visual Basic .NET, Second Edition

11. Identifying the Events
Text boxes and Label controls display their contents automatically - no special event is needed
The remaining objects are the three buttons: uiCalcButton, uiClearButton, and uiExitButton
Have the buttons perform their assigned tasks when they are clicked by the user
Programming with Microsoft Visual Basic .NET, Second Edition

12. Drawing a Sketch of the User Interface
In Western countries, organize the user interface so that the information flows either vertically or horizontally
In a vertical arrangement
The information flows from top to bottom
The essential information is located in the first column of the screen
Secondary information is placed in subsequent columns
Programming with Microsoft Visual Basic .NET, Second Edition

13. Drawing a Sketch of the User Interface (continued)
In a horizontal arrangement
The information flows from left to right
The essential information is placed in the first row of the screen
Secondary information placed in subsequent rows
You can use white space, a GroupBox control, or a Panel control to group related controls together
Programming with Microsoft Visual Basic .NET, Second Edition

14. Drawing a Sketch of the User Interface (continued)
If buttons appear in the interface, they should be positioned either in a row along the bottom of the screen, or stacked in either the upper-right or lower-right corner
Each text box and button control should be labeled so the user knows the control’s purpose
The Windows standard is to use sentence capitalization for identifying labels
Programming with Microsoft Visual Basic .NET, Second Edition

15. Building the User Interface Lesson B Objectives
Build the user interface using TOE chart and sketch
Follow the Windows standards regarding the use of graphics, color, and fonts
Set the BorderStyle property
Add a text box to a form
Programming with Microsoft Visual Basic .NET, Second Edition

16. Building the User Interface Lesson B Objectives (continued)
Lock the controls on the form
Assign access keys to controls
Use the TabIndex property
Programming with Microsoft Visual Basic .NET, Second Edition

17. Preparing to Create the User Interface
Maintain a consistent margin of two or three dots from the edge of the window
Position related controls on succeeding dots
Controls that are not part of any logical grouping may be positioned from two to four dots away from other controls
Try to create an interface that no one notices
Programming with Microsoft Visual Basic .NET, Second Edition

18. Including Graphics in the User Interface
The human eye is attracted to pictures before text; include a graphic only if it is necessary
If the graphic is for aesthetics only, use a small graphic and place it so as not to distract the user
Programming with Microsoft Visual Basic .NET, Second Edition

19. Including Different Fonts in the User Interface
Use 8, 10, or 12 point fonts for the elements in the user interface
Use only one or two font sizes
Use only one font type for all of the text
Avoid italic and underlining
Limit the use of bold text to titles, headings, and key items
Programming with Microsoft Visual Basic .NET, Second Edition

20. Including Color in the User Interface
Use either white, off-white, light gray, pale blue, or pale yellow for an application’s background, and use black for the text
Always use dark text on a light background
Never use a dark color for the background or a light color for the text
Limit the number of colors (other than white, black, and gray) to three
Programming with Microsoft Visual Basic .NET, Second Edition

21. The BorderStyle Property
BorderStyle property determines the style of a control’s border
Set the BorderStyle property of text boxes to Fixed3D
Set the BorderStyle property of labels that identify other controls to None
Set the BorderStyle property of labels that display program output to FixedSingle
Programming with Microsoft Visual Basic .NET, Second Edition

22. Adding a Text Box Control to the Form
A text box control provides an area in the form where the user can enter data
Add the missing text box control to the form and then set its properties
Programming with Microsoft Visual Basic .NET, Second Edition

23. Locking the Controls on a Form
Once you have placed all of the controls in the desired locations, lock them so you do not inadvertently move them
Once locked, you cannot move them until you unlock them; you can, however, delete them
Programming with Microsoft Visual Basic .NET, Second Edition

24. Assigning Access Keys
An access key allows the user to select an object by using the Alt key in combination with a letter or number
Each access key must be unique
You can assign an access key to any control that has a Caption property
Programming with Microsoft Visual Basic .NET, Second Edition

25. Assigning Access Keys (continued)
Place an & to the left of the desired letter in the Text property
To give keyboard access to a text box, assign an access key to its identifying label, then set the label’s TabIndex value to one less than the text box’s TabIndex value
Programming with Microsoft Visual Basic .NET, Second Edition

26. Setting the TabIndex Property
The TabIndex property determines the order in which a control receives the focus when the user presses either the Tab key or an access key while the application is running
When a control has the focus, it can accept user input
To determine the appropriate TabIndex settings for an application, make a list of the controls that can accept user input
Programming with Microsoft Visual Basic .NET, Second Edition

27. Setting the TabIndex Property (continued)
The list should reflect the order in which the user will want to access the controls
After listing the controls, assign each control in the list a TabIndex value, beginning with the number 0
You can use the Properties list to set the TabIndex property for each control; or, you can use the Tab Order option on the View menu
Programming with Microsoft Visual Basic .NET, Second Edition

28. Coding, Testing, Debugging, and Documenting the Application Lesson C Objectives
Use the TOE chart to code the application
Use pseudocode to plan an object’s code
Write an assignment statement
Use the Focus method
Programming with Microsoft Visual Basic .NET, Second Edition

29. Coding, Testing, Debugging, and Documenting the Application Lesson C Objectives (continued)
Include internal documentation in the code
Write arithmetic expressions
Use the Val and Format functions
Programming with Microsoft Visual Basic .NET, Second Edition

30. Coding the Application
Instructions are called code
The process of writing the instructions is called coding
Use pseudocode to help you plan the code
Internally document the code by placing an apostrophe before the comment in the Code window
Programming with Microsoft Visual Basic .NET, Second Edition

31. Coding the Clear Screen Button
According to the TOE chart, the Clear Screen button is assigned the task of clearing the screen for the next order
A zero-length string (empty string), is a pair of quote marks with nothing between them: “”
Assigning a zero-length string to the Text property of a control removes its contents
Programming with Microsoft Visual Basic .NET, Second Edition

32. Coding the Clear Screen Button (continued)
The pseudocode shown in Figure 2-25 represents the steps the Clear Screen button needs to prepare the screen for the next order
The programmer uses the pseudocode as a guide when coding the application
You use an assignment statement, which is simply a Visual Basic .NET instruction, to set the value of a property while an application is running
Programming with Microsoft Visual Basic .NET, Second Edition

33. Coding the Clear Screen Button (continued)
Figure 2-25: Steps for the Clear Screen button
Programming with Microsoft Visual Basic .NET, Second Edition

34. Assigning a Value to a Property During Run Time
Use the syntax [Me.]object.property=expression to set the value of an object’s property while an application is running
In an assignment statement, the equal sign (=) is called the assignment operator
The value of the expression on the right side of an = is assigned to the object and property that appears on the left side
Programming with Microsoft Visual Basic .NET, Second Edition

35. Using the Focus Method A method is a predefined procedure
The Focus method allows you to move the focus to a specified control
The syntax of the Focus method: [Me.]object.Focus()
Programming with Microsoft Visual Basic .NET, Second Edition

36. Internally Documenting the Program Code
Visual Basic .NET provides an easy way to document a program internally
Place an apostrophe (‘) before the statement you want treated as a comment
Visual Basic .NET ignores everything that appears after the apostrophe on that line
Programming with Microsoft Visual Basic .NET, Second Edition

37. Writing Arithmetic Expressions
The precedence numbers indicate the order in which Visual Basic .NET performs the operation in an expression
Operations with a lower precedence number are performed before operations with a higher precedence number
Programming with Microsoft Visual Basic .NET, Second Edition

38. Writing Arithmetic Expressions (continued)
Use parentheses to override the precedence
Use the integer division operator (\) to divide two integers and return the result as an integer
The modulus operator returns the remainder after integer division
Programming with Microsoft Visual Basic .NET, Second Edition

39. Writing Arithmetic Expressions (continued)
Figure 2-34: Arithmetic operators and their order of precedence
Programming with Microsoft Visual Basic .NET, Second Edition

40. Coding the Calculate Order Button
The Calculate Order button is responsible for:
Calculating both the total number of skateboards ordered and the total price of the order
Displaying the calculated amounts in the uiTotalBoardsLabel and uiTotalPriceLabel controls
The instructions to accomplish the Calculate Order button’s tasks should be placed in the button’s Click event procedure
Programming with Microsoft Visual Basic .NET, Second Edition

41. Coding the Calculate Order Button (continued)
Figure 2-35: Pseudocode for the Calculate Order button
Programming with Microsoft Visual Basic .NET, Second Edition

42. The Val Function
Like a method, a function is a predefined procedure that performs a specific task
The Val function temporarily converts a string to a number, and then returns the number
Syntax of the Val function is Val(string), where string is the string you want treated as a number
Programming with Microsoft Visual Basic .NET, Second Edition

43. Using the Format Function
Syntax: Format(expression, style)
Expression specifies the number, date, time, or string whose appearance you want to format
Style is either the name of a predefined Visual Basic .NET format style or a string containing symbols that indicate how you want the expression displayed
Programming with Microsoft Visual Basic .NET, Second Edition

44. Testing and Debugging the Application
Test an application by starting it and entering some sample data
Use both valid (expected) and invalid (unexpected) test data
Programming with Microsoft Visual Basic .NET, Second Edition

45. Testing and Debugging the Application (continued)
Debugging: locating errors in the program
Errors can be either syntax or logic
Most syntax errors are simply typing errors
Logic errors occur when you enter an instruction that does not give the expected results
Programming with Microsoft Visual Basic .NET, Second Edition

46. Assembling the Documentation
Assembling the documentation refers to putting in a safe place your planning tools and a printout of the application’s interface and code
Your planning tools include:
The TOE chart
Sketch of the interface
Flowcharts and/or pseudocode
Programming with Microsoft Visual Basic .NET, Second Edition

47. Summary Steps to create an OO application: Meet with the client
Plan the application
Build the user interface
Code the application
Test and debug the application
Assemble the documentation
Programming with Microsoft Visual Basic .NET, Second Edition

48. Summary (continued)
To control the border around a label control, set the label control’s BorderStyle property
To assign an access key to a control, type an ampersand (&) in the Text property of the control’s caption or identifying label
To set the tab order, set each control’s TabIndex property to a number that represents the order in which you want the control to receive the focus
Programming with Microsoft Visual Basic .NET, Second Edition

49. Summary (continued)
To assign a value to the property of an object while an application is running, use an assignment statement that follows the syntax: [Me.]object.property = expression
To document Visual Basic code with comments, begin the comment with an apostrophe (’)
To temporarily convert a string to a number, use the Val function
Programming with Microsoft Visual Basic .NET, Second Edition