1. Multiple Forms, Standard Modules, And Menus
Chapter 7
Multiple Forms,
Standard Modules,
And Menus

2. 7.1 Introduction

3. Chapter 7 Topics How to add multiple forms to a project
How to create a standard module
To hold procedures and functions
That is not associated with a specific form
Creating a menu system
Context menus
With commands and submenus that the user may select from

4. 7.2 Multiple Forms Visual Basic .NET Projects May Have Multiple Forms
If One of the Forms Is the Startup Object, It Is Displayed When the Project Executes
The Other Forms Are Displayed by Programming Statements

5. Form Names Each Form has its specific name
This name is set/changed with the Name Property
Each form also has a file name (.vb)
To change the file name:
Right click its entry in the Solution Explorer
Choose Rename

6. Adding a New Form Add New Item on the tool bar
The Add New Item dialog box appears
Click on Windows Form under Templates
Change the default name if you wish
Click Open

7. Switching between Design and Code
The Design window has the following tabs
frmMain.vb[Design] Form Design Itself
frmError.vb[Design] Error Form Design
frmMain.vb Main Code
frmError.vb Error Code

8. Classes and Instances
When you create a Form at design time, you are just creating a general description of a Form (It does not actually exist at that moment)
Analogy: It is a blueprint of a Form
An Instance must be created to actually have a Form at run time
Analogy: What the blueprint describes is actually built

9. Creating an Instance of a Form
It must be declared, syntax:
For example:
It is still not visible, but a form object has been instantiated
Refer to it using the variable errorForm
Dim ObjectVariable As New ClassName()
Dim errorForm As New frmError()

10. Modal Form/ShowDialog Method
When a Modal Form is displayed, no other form in the application can receive the focus until the modal form is closed
Use the ShowDialog Method to display a modal form:
errorForm.ShowDialog()

11. Modeless Form/Show Method
A Modeless Form allows the user to switch focus to another form in the same application
Use the Show Method to display a modeless form:
errorForm.Show()

12. Closing a Form
A form may close itself using the Close Method and referring to itself as "Me":
As in
Me.Close()
Private Sub btnClose_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles btnClose.Click
Me.Close()
End Sub

13. Hiding a Form Closing a Form eliminates it from memory
To simply make it not visible, use the Hide Method:
To bring it back use the ShowDialog() or Show() Methods
Me.Hide()

14. More About Modal and Modeless
statement;
messageForm.ShowDialog()
' Statements below will
' not execute until the
' Form is closed
statement;
messageForm.Show()
' Statements below will
' execute right after the
' Form is displayed

15. A Form's Load Event
The Load Event is triggered just before the form is initially displayed
If code needs to execute at this time, it must be contained in that event handling procedure:
Private Sub frmMain_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

16. A Form's Activated Event
The Activated Event is triggered when the user switches to the from from another form or another application
It is also triggered after the Load Event

17. A Form's Closing Event
This Event is triggered as the form is in the process of closing, but before it has closed
For instance, one might want to ask the user if they really want the form closed

18. A Form's Closed Event
The Closed Event is triggered after a form is closed
Note that it is now too late to prevent the Form from being closed (it is already)

19. Accessing Objects on a Different Form
When code in a form refers to an object, it is assumed that that object is in the same form
To refer to an object in another form, preface the object name with the variable name associated with that form:
Dim greetingForm As New frmGreeting()
greetingForm.lblMessage.Text = "Hello!"
greetingForm.ShowDialog()

20. Class-level Variables and Multiple Forms
Class-level variables are Private by default
This means they are not accessible by code in other forms
If you wish them to be, they must be declared with the Public qualifier:
Public total As Single
' Instead of the declaration
' Dim total As Single

21. Procedures Have Similar Access Rules
Procedures, by default, are Public
They can be accessed by code outside of their Form
To prevent this from happening, declare them to be Private

22. 7.3 Standard Modules
A Standard Module Contains Code - Declarations and Procedures - That Are Used by Other Files in a Project

23. Furthermore, Standard Modules
Are not associated with a Form
Contain no Event Procedures
Are saved in files with a .vb extension
Are used to hold code that is used by multiple Forms, or for command-line programs

24. Standard Module Syntax
Module ModuleName
[Module Contents]
End Module
A Module will contain Sub procedures and Functions, they can be
Private - only used by functions in that Module
Public - can be called from outside of the Module

25. Module Level Variables
These are declared within a Module
But not within Functions or Sub procedures in that Module
If declared Dim or Private, their scope is the Module (called module scope)
If declared Public, their scope is the application (called global scope)

26. Application with No Startup Form
Designate a Public Sub procedure named "Main" as the startup object
It must be in a Standard Module
When the application starts
No Form will be displayed
"Main" will be given control

27. You Use the Menu Designer to Create a Menu System
Visual Basic .NET Allows You to Create a System of Drop-down Menus for Any Form in Your Application
You Use the Menu Designer to Create a Menu System

28. Components of a Menu System, I
Menu Name
Shortcut Key
Checked Menu Command
Menu Command
Separator Bar
Submenu

29. Components of a Menu System, II
Menu Names - each drop-down menu has a name
Menu Command - the list of actions in the drop-down list
Shortcut Key - a key or combinations of keys to activate the command from the keyboard

30. Components of a Menu System, III
Disabled Menu Command - a command that is not applicable is grayed out (and is not selectable)
Checked Menu Command - some commands are toggles - checked when on, unchecked when off

31. Components of a Menu System, IV
Submenu - a command may lead to another menu
Separator Bar - a horizontal bar used to separate groups of commands

32. MainMenu Control
When used, the MainMenu control appears in the component tray (at the bottom of the Design Window)
It is composed of MenuItem Objects, such as:
Menu Name
Menu Command
Separator Bar
Sub-Menu Command

33. MenuItem Names Should begin with "mnu"
Then by convention are spelled, specifying their hierarchical position:
mnuFile
mnuFileSave
mnuFilePrint

34. MenuItem Text Properties
The text property is the text that appears on the menu
Plus if there is a access key, it is preceded with an ampersand, e.g. Object Name Text Property mnuFile &File mnuFileSave &Save mnuFileExit E&xit

35. Menu Designer
The Menu Designer speeds creation of menus with a fill in the box with text scheme:
Enter the
next menu
name
Enter first
command in
the File menu

36. Shortcut Keys
These are the key shortcuts that get one directly to the command action without going through the menu system (e.g., CTRL-C for Edit/Copy)
These are set via the Shortcut Property of each menu item

37. Disabled MenuItem Objects
The status of a menu item (enabled vs. disabled) is controlled by the Enabled property: True is Enabled
mnuEditPaste.Enabled = True

38. Adding Separator Bars
Either make the menu item’s Text property equal to "-" (hyphen)
Or right-click an existing menu item and select Insert Separator (it will be inserted above the menu item)

39. Inserting, Deleting, Rearranging Menu Items
To Insert a new menu item above an existing one, right-click to use the context sensitive menu
To Insert a new item at the end, use the Menu Designer
To Delete a menu item, right-click/Delete
To Rearrange menu items, click and drag them in the Menu Designer

40. Standard Menu Items
In general follow the conventions that the majority of application menu systems use
Specifically:
'File' is the leftmost menu item
The File menu has an 'Exit' command
'Help' is the rightmost menu item
The Help menu has an 'About' command

41. Context Menus
To establish a pop-up menu when a control is right-clicked:
Add the ContextMenu control to the component tray
Build the menu system with the Menu Designer
Add a Click Event procedure
Then associate the menu with the control by setting the control's ContextMenu property to the established menu