Lesson 3 — Menus, MDIs, and
Simple Loops
Microsoft Visual Basic
.NET, Introduction to
Programming
Objectives
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Design a menu bar with menus and
submenus.
Plan and document an application.
Use MDI forms.
Use For loops to write programs.
Vocabulary
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Access keys
Cascade
Definite loop
Indefinite loop
Loop
MainMenu tool
Multiple document interface (MDI)
Separator bar
Shortcut key
Tile
Menus
Menus are a common Windows tool that make it
easy to access commonly used commands. It is not
hard to imagine a Windows application with no menu
bar: all of your applications to this point have used
buttons. Menus are a more natural interface than
buttons because they allow you to group related
actions. Therefore, menus are an important part of
most Windows applications. The menu bar is found
at the top of the application window directly under
the title bar.
Visual Basic lets you create menus quickly and
easily.
Planning a Menu
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To what commands and options do users need
access?
In what order should the commands and options
appear?
What forms are required?
What information needs to be included on each
form?
From where will this information come?
Do the forms need to transfer information
elsewhere?
Basic Elements of a Menu
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Menus are made up of the menu bar, menu titles,
menu commands, submenu titles, and submenu
commands.
Menu titles appear on the menu bar at the top of the
form. When you click a menu title, its menu opens
and displays a list of menu commands or submenu
titles.
Menu items usually have associated access keys
that allow the user to quickly access them through
the keyboard.
Often, menu items also have shortcut key
combinations that let the user execute the command
without using the mouse.
Basic Conventions
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Start all menu titles and menu commands with a
capital letter.
File and Edit are usually the first menu titles on a
menu bar, and Help is usually the last one.
Use short, specific captions, preferably no more than
two words each.
Start the names of all menu items with the
three-letter prefix "mnu."
The MainMenu Tool
Did You Know?
In the early days of computers, the industry almost
died because of a lack of programmers. In the late
1950s and early 1960s, programmers used assembly
language, which is the obscure code-like language
one level above machine language, or binary. It
quickly became apparent that if something did not
happen to make programming easier, the industry
was doomed. To fill this need, high-level languages,
more easily understood by humans than computers,
were developed. The computers helped themselves
interpret these new languages.
Creating a
Menu in a
Windows
Application
Note
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There are a number of properties of the menu item
shown in the Properties window:
The Checked property, when True, displays a check
mark in front of the menu item. This is often used to
show that the menu item has already been selected.
This property can be set to True or False by program
code.
The Enabled property, when False, displays the item
grayed out, so the user cannot select it.
The Visible property, when False, makes the menu
item invisible to the user.
The Text property reflects the text entered in the
Type Here box on the form.
Menu Building in Progress
Tip
To reorder a menu, click and drag the
item to a new position. The other items
will make room as you drag.
Access Keys
You are probably familiar with access
keys and shortcut keys. Access keys
allow you to open a menu by pressing
the Alt key and then the designated
letter. Access keys also allow the user to
access a menu command once the
menu is open by continuing to hold the
Alt key and pressing its designated
letter.
Shortcuts
Shortcut keys are different. They run a
menu command immediately after the
shortcut key sequence is pressed.
Shortcut keys with which you may be
familiar are Ctrl+C for Copy and Ctrl+V for
Paste. You cannot assign a shortcut key to
a menu title.
Step-by-Step 3.3
Select the Open entry by clicking it. Click
again to edit the entry. Position the cursor
with the arrows and key an ampersand in
front of the word Open. This makes the letter
O the special access key.
Step-by-Step 3.3
In the Properties window, click the Shortcut
property. Click the list arrow to the right of the
entry and select CtrlO from the list. This sets
the shortcut for this menu command to
Ctrl+O. With the shortcut set, the user can
execute this command from the keyboard
without using the mouse or the access keys
to select and open the menu.
Menu Changes in Progress
Tip
Remember to name your objects as you
create them. Use short meaningful names
that start with the correct prefix. For menu
items, use the mnu prefix.
Adding Code to a Menu
When a user clicks a menu control, a Click event
occurs. All menu controls, with the exception of the
separator bar, recognize the Click event. Coding for
a menu Click event works the same as coding for
any other event procedure. You open the Code
window, choose the menu control from the Class
Name box on the left, and enter the code between
the Protected Sub and End Sub statements.
Another way to open a menu item’s Code window is
to double-click the menu item in the MainMenu tool.
Step-by-Step 3.4
'Change the color of the text in txtMenuTest to Black
Dim NewColor As New Color()
txtMenuTest.ForeColor = NewColor.Black()
'Check the Black submenu control
mnuEditColorBlack.Checked = True
'Uncheck the Blue submenu control
mnuEditColorBlue.Checked = False
'Uncheck the Red submenu control
mnuEditColorRed.Checked = False
Step-by-Step 3.4
'Change the color of the text in txtMenuTest to Blue
Dim NewColor As New Color()
txtMenuTest.ForeColor = NewColor.Blue
'UnCheck the Black submenu control
mnuEditColorBlack.Checked = False
'Check the Blue submenu control
mnuEditColorBlue.Checked = True
'Uncheck the Red submenu control
mnuEditColorRed.Checked = False
Step-by-Step 3.4
'Change the color of the text in txtMenuTest to Red
Dim NewColor As New Color()
txtMenuTest.ForeColor = NewColor.Red
'Uncheck the Black submenu control
mnuEditColorBlack.Checked = False
'Uncheck the Blue submenu control
mnuEditColorBlue.Checked = False
'Check the Red submenu control
mnuEditColorRed.Checked = True
Running a Program
Run the program by selecting Debug | Start
Without Debugging or pressing Ctrl+F5.
Colors
Visual Basic’s handling of colors is very
convenient for the programmer. When you
click the list arrow in the ForeColor property
in the Properties window, you get to choose
between three different color management
systems: you may select a color from among
System Colors, custom colors from a palette
of colors, or one of many predefined Web
colors.
Multiple Document Interface (MDI)
The multiple document interface (MDI) is another
common item found in Windows applications. The
MDI allows you to create an application that has
many forms that are contained within one main form.
Applications like Microsoft Word, where you can
open several different documents within the main
Word program, are MDIs.
The forms that make up an MDI (em-dee-eye)
project are referred to as parent and child forms. The
main application is referred to as the parent, and all
of the forms contained within the application are
called the children.
Parents and Children
There can be only one MDI parent form per
application. This cuts down on the possible
confusion that could result from having more than
one form in charge of the rest. You create an MDI
parent form by setting the appropriate property of the
form in the Properties window. When you create an
MDI form, the Properties window refers to it
specifically as an MDI form rather than just a form.
To have the application recognize that the other
forms are children of the MDI form, you set their
MDIChild property to True.
Programming Skills
A major problem that programmers run into is that
they tend to design for their own use. It may seem
obvious to you or another programmer how a
program should process data and how a user
accesses and enters that data. However, the
end-user typically does not have the same
perspective. Therefore, when designing a program, it
is essential that you plan for alternate approaches.
Murphy's law here is, “If there is one thing that would
crash a program, users will find it."
Creating an MDI Application
In order to create an MDI application, you must
create an MDI form. Creating an MDI form is similar
to creating any other new form. You populate the
form with controls from the Toolbox and build a
menu. Then change the form’s IsMDIContainer
property to True.
After the MDI container or parent form is created,
you create a template from which child forms are
created. You add a second form to the project and
populate it with controls from the Toolbox and
provide a menu. This second form is the template
used to create child forms while the application is
running.
Me
While the application is running, the parent
form can be referred to by the name Me. This
is a special variable in Visual Basic. Me holds
the name of the form that is currently active.
Thus, the Me takes different values
depending on the active form.
Step-by-Step 3.5
'Create a new instance (copy) of Form2
Dim NewMDIChild As New Form2()
'Designate the Child form's parent
NewMDIChild.MDIParent = Me
'Display the new form.
NewMDIChild.Show()
Cascaded
Child
Forms
Child Forms
Tiled
Horizontally
Child
Forms
Tiled
Vertically
Child Form Icons Arranged on the
Parent Form
Step-by-Step 3.6
Form1.LayoutMDI(MDILayout.Cascade)
Form1.LayoutMDI(MDILayout.TileHorizontal)
Form1.LayoutMDI(MDILayout.TileVertical)
Form1.LayoutMDI(MDILayout.ArrangeIcons)
Adding a Form
A unique form is created in the design phase
of the project. Even though you work with the
form in the design phase, the form must be
called into existence by program code. If the
name of the added form is About.vb, the
code to create a new instance of the form is
Dim NewAbout As New About().
The New Form
Once a new form is added, the Show method
of the form is called to display it. The Hide
method hides the form without unloading it
from memory. If necessary, the form’s Unload
method is used to unload the form from
memory. Unlike the child forms that appear
wholly contained within the parent form, the
new form is displayed independently.
Simple Loops
Executing the same statements over and over at
almost inconceivable speeds is what makes
computers so powerful. Visual Basic has a number
of statements designed to control this repetition.
The first is the For loop. A loop is any program
statement that causes the repetition of a group of
statements. This is called a definite loop because
its starting value, the upper limit, and the number of
repetitions is generally known before the loop
begins.
For loop
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The syntax of the For loop is:
For control variable = starting value To upper limit Step increment
body of the loop
Next
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An example is:
For x = 1 To 100 Step 2
'The statements that make up the body of the loop go here.
Next x
Examples
For x = LowerLimit To 5 * LowerLimit
…
Next x
For Item = 1 to 25
…
Next Item
Examples
For x = -5 To 5 Step 0.01
…
Next x
For Pounds = 8 to 24
Time = Pounds * 17
…
Next Pounds
Backward
Loops can count forward or backward.
For x = 10 To 1 Step -1
…
Next x
Important
The value of the control variable should not
be changed in the body of a For loop. The
value is controlled by the For loop itself.
Step-by-Step 3.8
'Declare the necessary variables.
Dim StartingValue, UpperLimit, Increment As Integer
Dim ControlVariable As Integer
Dim DirectCost, FixedCost, TotalCost As Decimal
'Collect information from the TextBoxes.
DirectCost = txtDirectCost.Text.ToDecimal
FixedCost = txtFixedCost.Text.ToDecimal
Step-by-Step 3.8
'Collect information from the user.
StartingValue = CInt(InputBox("Enter the starting value:"))
UpperLimit = CInt(InputBox("Enter the upper limit:"))
Increment = CInt(InputBox("Enter the increment:"))
For ControlVariable = StartingValue To UpperLimit Step Increment
TotalCost = DirectCost * ControlVariable + FixedCost
MessageBox.Show("The cost at " & ControlVariable.ToString _
& " items is:" & CrLf & TotalCost.ToString)
Next ControlVariable
Communication Skills
In creating and editing programs, you will
often forget why you did things a certain way
or why a particular "fix" was used. That is why
it is essential that you document your
programs with explanations and dates for
later reference. You may have already
noticed that you have been using internal
comments. This helps later when revisions
are made and when the final documentation
is done.
Summary
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Menus make it easier for users to execute
commands in their programs.
The MainMenu tool makes creating
professional-looking menus easy.
Shortcut keys and access keys help speed up
access to commonly used menu commands.
The multiple document interface is made up of one
parent form that contains many child forms.
Summary
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Previously created forms can be added from
other projects.
The MDILayout method provides flexibility to
the user to display child forms in different
ways.
The For statement is used to build definite
loops that repeat statements a fixed number
of times.