1. Programming In Visual Basic .NET
Chapter 5 Menus, Common Dialog Boxes, Sub Procedures and Function Procedures
Programming In
Visual Basic .NET

2. <ALT><F>
Menu
<ALT><F>
Menu Items
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3. Menus
Menu Bar
Contains menus which drop down to display list of menu items
Each item has a name and text property
Each item has a click event
Add MainMenu control to form
Appears in the Component Tray, below form, where nondisplay controls are shown
Words "Type Here" appear at the top of the form
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4. Menus (continued) Type first Menu here
MainMenu Control appears in Component Tray
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5. Defining Menus
To create the menus simply type where the words "Type Here" appear at the top of the form
Include & symbol as you type to indicate keyboard access keys
You are actually entering the Text property for a MenuItem object
Change MenuItem object names in the Properties window and follow consistent naming conventions
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6. Submenus Pop up to the right of a menu item
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
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7. Submenus (continued)
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8. Separator Bars Used for grouping menu items according to their purpose
Visually represented as a bar across the menu
Create using one of two methods
Typing a single hyphen for the text
Right-click on Menu Designer where you want a separator bar and choose Insert Separator
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9. Coding for Menu Items
Double-click any menu item to open the item’s click event procedure
Write code for the click event procedure
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10. Modifying Menu Items Right-click the Menu Bar to: Delete Insert New
Insert Separator
Edit Names
Displays menu item Name property rather than Text property on form
Drag and Drop menu items to new locations
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11. Menu Properties Enabled property, True/False
Checked property, True/False
Used to indicate current state of menu item that can be turned on and off
Create keyboard shortcuts
In Properties window for menu item, select the Shortcut property
Make choice from drop-down list
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12. Standards for Windows Menus
Follow Windows standards for applications
Include keyboard access keys
Use standards for shortcut keys, if used
Place File menu at left end of menu bar and end File menu with Exit
Help, if included, is placed at right end of menu bar
File Edit View Format Help
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13. Common Dialog Boxes Predefined standard dialog boxes for:
File Opening and Saving
Font and Color selection
Printing and Previewing
Add appropriate Common Dialog control to form
Appears in the Component Tray
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14. Common Dialog Controls
OpenFileDialog
SaveFileDialog
FontDialog
ColorDialog
PrintDialog
PrintPreviewDialog
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15. Common dialog controls
Component tray
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16. Displaying a Windows Common Dialog Box
Use ShowDialog method to display the common dialog box at run time
ShowDialog only displays the dialog, it does not do anything else
ColorDialog1.ShowDialog( )
FontDialog1.ShowDialog( )
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17. With OpenFileDialog1 .ShowDialog() End With Code
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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
Code must be written to apply the selected color to the object(s)
titleLabel.BackColor = ColorDialog1.Color
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19. Color and Font Dialogs
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20. 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
FontDialog1.Font = subTotalLabel.Font or ColorDialog1.Color = Me.BackColor
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21. Creating Context Menus
Shortcut menus that pop up when you right-click
Are specific to the component to which user is pointing, reflecting options available for that component or situation
A context menu does not have a top level menu
Application can have multiple context menus
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22. Creating Context Menus (continued)
Add ContextMenu component to the form
Appears in the Component Tray
Click on the words "Context Menu", at the top of the form, the words "Type Here" appear
Click on the words "Type Here" and proceed as you did for the main menu
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23. Connecting the Context Menu to a Form or Object
Set the form or object’s ContextMenu property to the name of the ContextMenu
If there is more than one context menu defined, choose from the list
Add to the Handles clause of a MainMenu item to use the same procedure for a related ContextMenu item
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24. 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)
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25. Creating a New Sub Procedure
In the Editor window enclose the lines of code with a set of Private 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
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26. Passing Arguments to Procedures (page 205)
Declare variable as local and pass to any called procedures
If a sub procedure names an argument, any call to the procedure must supply the argument
Name of local variable does not need to match name in sub procedure argument list
Number of arguments, sequence and data type must match
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27. Passing Arguments ByVal or ByRef
ByVal (default)
Sends a copy, original cannot be altered
ByRef
Sends a reference to the memory location where the original is stored and therefore the original can be altered
Examples page 206
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28. Sub Procedure Calling Procedure Sub Procedure Example
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
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29. Writing Function Procedures
In the Editor window enclose the lines of code with Private Function( ) and End Function statements
To use the Function, Call it by using it in an expression
Pass arguments ByVal or ByRef
Private Function FunctionName( ) As Datatype
' Statements to execute.
End Function
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30. 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
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31. Function Function Example Calling Procedure
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
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32. 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
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33. 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
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34. © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.