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McGraw-Hill 2009 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 5

Menus, Common Dialog

Boxes, Sub Procedures,

and

Function Procedures


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5-2

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 andfunction procedures and call the procedures from

other locations.


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5-3

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 toexecute a procedure

Menu items are controls with properties and events.

Easy to create menus for a Windows form using

the Visual Studio environments Menu Designer Menus will look and behave like standard

Windows menus.


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5-4

Defining Menus (1 of 2)

MenuStrip component isadded to a form.

MenuStrip is a container towhich ToolStripMenuItems,

ToolStripComboBoxes,

ToolStripSeparators, and

ToolStripTextBoxes can beadded.


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5-5

Defining Menus (2 of 2)

The MenuStrip componentappears in the component tray

below the form and the Menu

Designer allows you to begin

typing the text for the menu

items.


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5-6

The Text Property

Holds the words that appear on the screen like theText property of a button or label

To conform to Windows standards, the first menus Text

property should be File, with a keyboard access key. Use the ampersand (&) in the text to specify the keyto use for keyboard access.

Enter and change the Text property for each menu and

menu item using the Menu Designer or make thechanges in the Text property using the Properties

window.


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5-7

The Name Property

The File menu item that is added is automaticallynamed FileToolStripMenuItem.

The items are named so well that there wont be a

need to change the Name property of any menucomponent.

If the Text property is changed for any menuitem, the item is not automatically renamed; it

will need to be renamed.


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5-8

The MenuStrip Items Collection

ToolStripMenu Items in the collection can bedisplayed, reordered, added, and deleted using the

Items Collection Editor.


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McGraw-Hill 2009 The McGraw-Hill Companies, Inc. All rights reserved. 5-9

Submenus

A filled triangle to theright of the menu item

indicates the existenceof a submenu.

Create submenus bymoving to the right of a

menu item and typingthe next item's text.


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Separator Bars

Used for grouping menuitems according to their

purpose

Visually represented asa bar across the menu To create a separator

bar, add a new menu

item and click on itsdrop-down arrow.


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Menu Properties

Enabled property, True/False can be set at designor run time

Checkedproperty, False/True can be set at designor run time

Used to indicate that an option is selected Setting keyboard shortcuts

Select the menu item and in Properties window for menuitem, select the ShortcutKeys 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 the File menu at left end of menu bar and endFile menu with the Exit command. 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: Specifying colors and fonts Printing, opening, and saving

Add appropriate Common Dialog componentsto display the dialog boxes that are provided aspart of the Windows environment.

To use a common dialog component, add thecomponent to the form, placing it in the componenttray.


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Common Dialog Tools

Pointer ColorDialog FontBrowserDialog FontDialog

OpenFileDialog SaveFileDialog


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Displaying a Windows Common Dialog Box

Use ShowDialogmethod to display the commondialog box at run time.

ShowDialog only displays the dialog.

ColorDialog1.ShowDialog( )

FontDialog1.ShowDialog( )


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Modal versus Modeless Windows

A dialog box is said to be modal when it stays ontop 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 aresponse.

Use the Show method to display a modeless window.


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Using the Information from the Dialog

Box

Code must be written to retrieve and use the choicemade 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 propertyand can be assigned to another object such as acontrol.

titleLabel.BackColor = .ColorDialog1.Color


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Setting Initial Values

Before executing the ShowDialog method,assign the existing values of the object'sproperties that will be altered.

When the dialog box appears, the currentvalues will be selected.

If the user presses Cancel, property settings forthe objects will remain unchanged.

FontDialog1.Font = SubTotalLabel.Font or

ColorDialog1.Color = .BackColor


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Creating Context Menus

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.


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Writing General Procedures

A general procedure is reusable code that can becalled 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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Passing Arguments to Procedures

Declare variable as local and pass to any calledprocedures (can be module level, but it makes thevariable visible to all other procedures)

If a sub procedure names an argument, any call tothe procedure must supply the argument.

Name of the argument does not have to be the samein both locations.

Number of arguments, sequence, and data typemust match.


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Creating a New Sub Procedure

In the Editor window, enclose the lines of codewith a set of Sub and End Sub statements.

To use the Sub Procedure, call it from anotherprocedure.

Code in a Sub Procedure cannot be executedunless called from another procedure.

Private Sub ProcedureName( )

' Statements in the procedure.

End Sub


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Sub Procedure Example

Private Sub SelectColor(incomingColor As Color)With ColorDialog1

.Color = incomingColor

.ShowDialog( )

End With

End Sub

Private Sub ChangeTitleButton_Click( )

Dim originalColor As Color

originalColor = TitleLabel.ForeColor

SelectColor(originalColor)TitleLabel.ForeColor = ColorDialog1.Color

End Sub

Sub Procedure

Calling

Procedure


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Passing Arguments ByVal or ByRef

ByVal valueSends a copy of the arguments value; original

cannot be altered.

ByRefreferenceSends a reference to the memory location where

the original is stored and therefore the procedure

may change the arguments value; original can bealtered

If not specified, arguments are passed by value.


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Writing Function Procedures

In the Editor window, enclose the linesof code with Private Function( ) and End Function

statements.

Since the procedure returns a value, a data type for thevalue 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


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Returning the Result of a Function

To return a value to the calling procedure, set up areturn value.

The return value will be placed by VB in a variablewith the SAME name as the Function's name.

--OR--

Use the Return statement to return the value.


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Function Example

Private Sub CalculateButton_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles CalculateButton.Click

Dim SalesDecimal As DecimalSalesDecimal = Decimal.Parse(SalesTextBox.Text)

CommissionLabel.Text = Commission(SalesDecimal).ToString( "C")

End With

End Sub

Calling

Procedure

Private Function Commission(ByVal SalesAmountDecimal As Decimal) _As Decimal

If SalesAmountDecimal < 1000D Then

Commission = 0D

ElseIf SalesAmountDecimal


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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

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


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Breaking Calculations into Smaller Units

Projects with many calculations are easierto understand and write if calculations are

broken into small units.

Each unit should perform one programfunction or logic block.

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