Chapter 5
Menus, Common Dialog
Boxes, Sub Procedures
and
Function Procedures
Programming In
Visual Basic .NET
Menu
<ALT><F>
Menu Items
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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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Menus (continued)
Type first Menu here
MainMenu Control
appears in
Component Tray
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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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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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Submenus (continued)
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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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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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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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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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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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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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Common Dialog Controls
•
•
•
•
•
•
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OpenFileDialog
SaveFileDialog
FontDialog
ColorDialog
PrintDialog
PrintPreviewDialog
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Common dialog controls
Component tray
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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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With OpenFileDialog1
.ShowDialog()
End With
Code
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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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Color and Font Dialogs
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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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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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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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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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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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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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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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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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Sub Procedure Example
Private Sub SelectColor(incomingColor As Color)
With ColorDialog1
.Color = incomingColor
Sub Procedure
.ShowDialog( )
End With
End Sub
Private Sub changeTitleButtonColor_Click( )
Dim originalColor As Color
originalColor = titleLabel.ForeColor
SelectColor(originalColor)
titleLabel.ForeColor = ColorDialog1.Color
End Sub
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Calling
Procedure
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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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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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Function Example
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( )
Calling
Dim salesDecimal As Decimal
Procedure
salesDecimal = Decimal.Parse(salesTextBox.Text)
commissionLabel.Text = Commission(salesDecimal.ToString("C"))
End Sub
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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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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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