Chapter 5
Menus, Common
Dialog Boxes, Sub
Procedures, and
Function Procedures
McGraw-Hill
Copyright © 2011 by The McGraw-Hill Companies, Inc. All Rights Reserved.
Objectives
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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.
5-2
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
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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.
5-3
Defining Menus (1 of 2)
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MenuStrip component is
added to a form.
MenuStrip is a container to
which ToolStripMenuItems,
ToolStripComboBoxes,
ToolStripSeparators, and
ToolStripTextBoxes can be
added.
5-4
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.
5-5
The Text Property
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Holds the words that appear on the screen — like the
Text property of a button or label
To conform to 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.
5-6
The Name Property
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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.
5-7
The MenuStrip Items Collection
•
ToolStripMenu Items in the collection can be
displayed, reordered, added, and deleted using the
Items Collection Editor.
5-8
Submenus
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•
A filled triangle to the
right of the menu item
indicates the existence
of a submenu.
Create submenus by
moving to the right of a
menu item and typing
the next item's text.
5-9
Separator Bars
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•
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.
5-10
Menu Properties
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•
•
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 ShortcutKeys property.
• Make choice from drop-down list.
5-11
Standards for Windows Menus
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•
•
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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
5-12
Common Dialog Boxes
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•
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.
5-13
Common Dialog Tools
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Pointer
ColorDialog
FontBrowserDialog
FontDialog
OpenFileDialog
SaveFileDialog
5-14
Displaying a Windows Common Dialog Box
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Use ShowDialog method to display the common
dialog box at run time.
ShowDialog only displays the dialog.
ColorDialog1.ShowDialog( )
FontDialog1.ShowDialog( )
5-15
Modal versus Modeless Windows
•
A dialog box is said to be modal when 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.
• A modeless window can be ignored by the user.
5-16
Using the Information from the Dialog Box
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•
Code must be written to retrieve and use the choice
made by the user in the common dialog box.
Example
• Color Dialog is 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.
TitleLabel.BackColor = .ColorDialog1.Color
5-17
Setting Initial Values
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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 = .BackColor
5-18
Creating Context Menus
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Shortcut menus that pop up when you right-click
Items are specific to the component to which the
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.
5-19
Writing General Procedures
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•
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A general procedure is reusable code that can be
called from multiple procedures.
Useful for breaking down large sections of code into
smaller units
Two types
• A Sub Procedure performs actions.
• A Function Procedure performs actions AND returns a
value (the return value).
5-20
Passing Arguments to Procedures
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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.
5-21
Creating a New Sub Procedure
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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
5-22
Sub Procedure Example
Private Sub SelectColor(incomingColor As Color)
With ColorDialog1
.Color = incomingColor
.ShowDialog( )
Sub
End With
End Sub
Private Sub ChangeTitleButton_Click( )
Dim OriginalColor As Color
OriginalColor = TitleLabel.ForeColor
SelectColor(originalColor)
TitleLabel.ForeColor = ColorDialog1.Color
End Sub
Procedure
Calling
Procedure
5-23
Passing Arguments ByVal or ByRef
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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 value; original can be
altered
If not specified, arguments are passed by value.
5-24
Writing Function Procedures
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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.
Private Function ProcedureName( ) As Datatype
' Statements to execute.
End Function
5-25
Returning the Result of a Function
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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.
5-26
Function Example
Private Function Commission(ByVal SalesAmountDecimal As Decimal) _
As Decimal
If SalesAmountDecimal < 1000D Then
Commission = 0D
ElseIf SalesAmountDecimal <= 2000D Then
Commission = 0.15D* SalesAmountDecimal
Else
Function
Commission = 0.2D * SalesAmountDecimal
End If
End Function
Private Sub CalculateButton_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles CalculateButton.Click
Calling
Dim SalesDecimal As Decimal
Procedure
SalesDecimal = Decimal.Parse(SalesTextBox.Text)
CommissionLabel.Text = Commission(SalesDecimal).ToString("C")
End With
End Sub
5-27
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
Dim RatePerMonthDecimal As Decimal
RatePerMonthDecimal = RateDecimal / 12D
' Calculate and set the return value of the function.
Payment = Convert.ToDecimal((AmountDecimal * RatePerMonthDecimal)
/ ((1 - (1 / (1 + RatePerMonthDecimal) ^ (TimeDecimal * 12D)))))
End Function
5-28
Breaking Calculations into Smaller Units
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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.
5-29
Writing Function Procedures
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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.
Private Function ProcedureName( ) As Datatype
' Statements to execute.
End Function
5-30
New OEA Form
OBJECT
EVENT
TASK(S)
PROCEDURE
PARAMETER(S)
TASK(S)
<type – name>
5-31
OEA – Procedure Example
PROCEDURE
PARAMETER(S)
TASK(S)
Sub – Clear
None
Clear input fields
Clear output fields
Function CalculateItemAmount
Quantity
Price
Calculate Item Amount (Q * P)
5-32