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2. Menus, Common Dialog Boxes, Sub Procedures and Function Procedures5
Chapter
Menus, Common Dialog Boxes, Sub Procedures and Function Procedures
McGraw-Hill
© 2006 The McGraw-Hill Companies, Inc. All rights reserved.

3. Objectives Create menus and submenus for program control
Display and use the Windows common dialog boxes
Create context menus for controls and the form
Write reusable code in sub procedures and function procedures and call the procedures from other locations

4. Menus
Menu Bar
Contains menus which drop down to display list of menu items
Can be used in place of or in addition to buttons to execute a procedure
Menu items are controls with properties and events
Easy to create menus for a Windows form using the Visual Studio environment’s Menu Designer
Menus will look and behave like standard Windows menus
Menus are used quite extensively while working with the computer

5. Defining Menus (1 of 2) MenuStrip component is added to a form
MenuStrip is a container to which ToolStripMenu Items, ToolStripComboBoxes, ToolStripSeparators, and ToolStripTextBoxes can be added

6. Defining Menus (2 of 2) The MenuStrip component
appears in the component tray
below the form and the Menu
Designer allows you to begin
typing the text for the menu
items.
To create the menus simply type where the words "Type Here" appear at the top of the form
Each time the text for a new menu is entered a ToolStripMenuItem is automatically added to the MenuStrip’s Items collection

7. The Text Property
Holds the words that appear on the screen – like the Text property of a button or label
To conform Windows standards the first menu’s Text property should be File, with a keyboard access key
Use the ampersand (&) in the text to specify the key to use for keyboard access
Enter and change the Text property for each menu and menu item using the Menu Designer or make the changes in the Text property using the Properties window
When typing the words for a menu or menu item the Text property is being entered for the item

8. The Name Property
The File menu item that is added is automatically named FileToolStripMenuItem
The items are named so well that there won’t be a need to change the Name property of any menu component
If the Text property is changed for any menu item, the item is not automatically renamed; it will need to be renamed
Another big improvement to VB 2005 menus is that the Menu Designer is now smart enough to give good names to the menu items

9. The MenuStrip Items Collection
ToolStripMenu Items in the collection can be displayed, reordered, added, deleted using the Items Collection Editor
As new menus are created using the Menu Designer, each menu is added to the Items collection that belongs to the MenuStrip

10. Submenus
Filled triangle to the right of the menu item indicates to the user the existence of a submenu
Create submenus by moving to the right of a menu item and typing the next item's text
The drop-down list of items below a menu name is called a menu
When an item on the menu has another list of items that pops up, the new list is calla submenu

11. Separator Bars Used for grouping menu items according to their purpose
Visually represented as a bar across the menu
To create a separator bar, add a new menu item and click on its drop-down arrow

12. Menu Properties
Enabled property, True/False-can be set at design or run time
Checked property, False/True-can be set at design or run time
Used to indicate that an option is selected
Setting keyboard shortcuts
Select the menu item and In Properties window for menu item, select the ShortcuKeyst property
Make choice from drop-down list
By default, all new menu items have their Enabled property set to True
An enabled menu item appears in black test and is available for selection whereas the grayed out or disabled (key term) items are not available (False)
A menu item may contain a check mark beside it (indicating that the item is checked—by default the Checked property is set to False
Many computer users prefer to use keyboard shortcuts for selecting menu items

13. Standards for Windows Menus
Follow Windows standards for applications
Include keyboard access keys
Use standards for shortcut keys, if used
Place the File menu at left end of menu bar and end File menu with the Exit command
Help, if included, is placed at right end of menu bar
File Edit View Format Help
When applications are written to run under Windows, programs should follow the Windows standards
Plan menus so that they look like other Windows programs

14. Common Dialog Boxes Predefined standard dialog boxes for:
Specifying colors and fonts
Printing, opening, and saving
Add appropriate Common Dialog components to display the dialog boxes that are provided as part of the Windows environment
To use a common dialog component, add the component to the form, placing it in the component tray

15. Common Dialog Tools Pointer ColorDialog FontBrowserDialog FontDialog
OpenFileDialog
SaveFileDialog

16. Displaying a Windows Common Dialog Box
Use ShowDialog method to display the common dialog box at run time
ShowDialog only displays the dialog
ColorDialog1.ShowDialog( )
FontDialog1.ShowDialog( )

17. Modal versus Modeless Windows
A dialog box is said to be modal - means that it stays on top of the application and must be responded to
Use the ShowDialog method to display a dialog box-it is a window displayed modally
Modeless windows do not demand that there is a response
Use the Show method to display a modeless window
You have probably noticed that when you display a Windows dialog box it remains on top until you respond to it
But in many applications you can display additional windows and switch back and forth between windows

18. Using the Information from the Dialog Box
Code must be written to retrieve and use the choice made by the user in the common dialog box
Example
Color Dialog displayed
User selects color and clicks OK-the selected color is stored in a property that can be accessed
Color that is selected is stored in the Color property and can be assigned to another object such as a control
You can also use the Font Dialog Box in much the same way and assign Font properties to the Front property of other objects on a form
titleLabel.BackColor = ColorDialog1.Color

19. Setting Initial Values
Before executing the ShowDialog method, assign the existing values of the object's properties that will be altered
When the dialog box appears, the current values will be selected
If the user presses Cancel, property settings for the objects will remain unchanged
When a common dialog box for colors or fonts appears, what color or font do you want to display? It’s best to assign initial values before showing the dialog box
FontDialog1.Font = .subTotalLabel.Font or ColorDialog1.Color = .BackColor

20. Creating Context Menus
Shortcut menus that pop up when you right-click
Items are specific to the component to which user is pointing, reflecting options available for that component or situation
A ContextMenuStrip component is added and appears in the component tray below the form
A context menu does not have a top-level menu, only menu items
Application can have multiple context menus
Context menus can be added to applications
Creating a context menu is similar to creating a menu

21. Writing General Procedures
A general procedure is reusable code which can be called from multiple procedures
Useful for breaking down large sections of code into smaller units
Two types
Sub Procedure performs actions
Function performs actions AND returns a value (the return value)
Often programming situations exist in which multiple procedures perform the same operation—this conidtion can occur when the user can select either a button or a menu item to do the same thing
Rather than retyping the code reusable code in a general procedure can be written and call it from both event procedures

22. Passing Arguments to Procedures
Declare variable as local and pass to any called procedures – (can be module level but it makes the variable visible to all other procedures)
If a sub procedure names an argument, any call to the procedure must supply the argument
Name of the argument does not have to be the same in both locations
Number of arguments, sequence and data type must match
At time it may be necessary to use the value of a variable in one procedure and then again in a second procedure that is call from the first

23. Creating a New Sub Procedure
In the Editor window enclose the lines of code with a set of Sub and End Sub statements
To use the Sub Procedure, call it from another procedure
Code in a Sub Procedure cannot be executed unless called from another procedure
Private Sub ProcedureName( )
' Statements in the procedure.
End Sub
VB.NET has choices other than Private for the access, such as Public, Friend, and Protected—Private can be used for all general procedures (key term)

24. Sub Procedure Example Sub Procedure Calling Procedure
Private Sub SelectColor(incomingColor As Color)
With ColorDialog1
.Color = incomingColor
.ShowDialog( )
End With
End Sub
Sub Procedure
Private Sub changeTitleButtonColor_Click( )
Dim originalColor As Color
originalColor = titleLabel.ForeColor
SelectColor(originalColor)
titleLabel.ForeColor = ColorDialog1.Color
End Sub
Calling
Procedure

25. Passing Arguments ByVal or ByRef
ByVal -value
Sends a copy of the argument’s value, original cannot be altered
ByRef -reference
Sends a reference to the memory location where the original is stored and therefore the procedure may change the argument’s original value can be altered
If not specified arguments are passed by value
When passing a value to a procedure it may be passed ByVal or ByRed

26. Writing Function Procedures
In the Editor window enclose the lines of code with Private Function( ) and End Function statements
Since the procedure returns a value a data type for the value must be specified
To use the Function, Call it by using it in an expression
Pass arguments ByVal or ByRef
Programmers may need to calculate a value that will be needed in several different procedures or programs
Functions also can be declared as Public, Protected, or Friend (introduced in later chapter)
Private Function FunctionName( ) As Datatype
' Statements to execute.
End Function

27. Returning the Result of a Function
To return a value to the calling procedure set up a return value
The return value will be placed by VB in a variable with the SAME name as the Function's name
--OR--
Use the Return statement to return the value
The main difference between coding a function procedure and coding a sub procedure is that in a function procedure a return value must be set; the return value is palced in a variable that VB names with the same name as the function name

28. Function Example Calling Procedure Function
Private Function Commission(ByVal salesAmountDecimal As Decimal) _
As Decimal
If salesAmountDecimal < 100D Then
Commission = 0D
Else
Commission = 0.15 * salesAmountDecimal
End If
End Function
Function
Private Sub calculateButton_Click( )
Dim salesDecimal As Decimal
salesDecimal = Decimal.Parse(salesTextBox.Text)
commissionLabel.Text = Commission(salesDecimal.ToString("C"))
End Sub
Calling
Procedure

29. Functions with Multiple Arguments
Functions can receive one or more arguments (values)
Sequence and data type of arguments in Call must exactly match arguments in function header
Private Function Payment(ByVal rateDecimal As Decimal, _ ByVal timeDecimal As Decimal, ByVal amountDecimal _ As Decimal) As Decimal
paymentLabel.Text = Payment(Decimal.Parse(rateTextBox.Text), _ Decimal.Parse(yearsTextBox.Text), _ Decimal.Parse(principalTextBox.Text)).ToString( ) End Function

30. Breaking Calculations into Smaller Units
Projects with many calculations are easier to understand and write if calculations are broken into small units
Each unit should perform one program function or logic block