1. Multi-Form Applications Things You Need to Know
ISM 3005 Course Introduction
Topics
Multi-Form Applications
Things You Need to Know
Application Form Management
When the Application Ends
Opening Another Form and Returning
Communicating Between Forms
Dialogs
“Never let a computer know you’re in a hurry”
Unknown 2

2. Multi-Form Applications
Most applications require multiple forms
More than one task performed under the application umbrella
Multi-step tasks
Too much information to fit on a single form
The user should almost never be able to switch between different concurrently open windows

3. Multi-Form Applications
You must take careful control over forms
What the user sees
When the application ends
Which form opens first
Which forms are open at any particular time
Which forms are open and visible
Which forms are open and invisible
You need to avoid leaving an application running but with no visible forms

4. Things You Need to Know
How to create a new form
How to change the startup form for a project
How closing forms can end the program
How closing forms can leave a program running with no visible form
How to set values on one form from another one
How to create an object variable referencing a form and use it to open and communicate with a form
The difference between referencing an object variable version of a form and the form directly

5. Things You Need to Know (cont.)
How to use Dialog Boxes and predefined form types
How to create a custom dialog box form
How to call a custom dialog form from multiple forms and have the dialog update the proper calling form
How to set up a splash screen

6. Planning the Project’s Navigation
Top-Down menu navigation
All other forms are reached from the main menu
Navigation always returns to the main menu
May have subordinate levels of menu
Consider only letting top level menu end the application
Other forms will Close
Return to the top menu

7. Planning the Project’s Navigation (cont.)
Multi-step task requires navigating through a sequence of forms
Return to top level menu from a different form than the one directly reached

8. Planning the Project’s Navigation (cont.)
Multiple Paths
Some forms may be reached from different forms

9. Planning the Project’s Navigation (cont.)
The navigation approaches needed have implications for how you open and close forms
Some needs may have multiple techniques
Some techniques may not be suitable for some navigation needs

10. Form File Names
When a new project is created it will automatically get a form called Form1 with a file name of Form1.vb
The only way to take control of the form’s file name is to delete the default form and create a new one
Set the new form’s name when it is created
This will also be the file name
Change the Project Startup Form
Choose Project | Properties from the menu

11. 1
Adding a New Form 2
Add a new form in the Solution Explorer
Right-click the project
Select Add
Select Windows Form…
Set the form’s name and file name in the resulting dialog
(If the application is large enough you should use folders to organize it) 3

12. Project Properties
Use the Project | Properties … menu to set project form properties
Start up form
Always set this if you remove Form1 as first form
Shutdown mode
Determines when form closing ends the application
I recommend “When Last Form Closes” choice

13. Showing a Form
Three techniques to make a form visible
FormName.Show
Any code in the procedure following this statement will continue to execute
User can click on either form
FormName.ShowDialog
Execution of code in the current procedure is paused until the called form is closed
User cannot address any other form
FromName.Visible = True (do not use)

14. Navigation Techniques
You should almost never have more than one form active and available to the user at a time
If Form A calls Form B you can make Form A unavailable in four ways
Close Form A (FormA.Close)
Make Form A invisible (FormA.Visible = False)
Disable Form A (FormA.Enabled = False)
Show Form B “modally” in dialog form FormB.ShowDialog
Approaches 1 & 2hide Form A while 3 & 4 leave Form A visible but unavailable

15. Navigation Techniques (cont.)
If you close the last open form you will end the application
If you set a calling form (Form A) to be invisible or disabled — and — you close Form B
You can leave the application running but with no visible form for the user to navigate from
User must use Task Manager to end a compiled program
Or stop debugging in development mode
Some approaches can leave you with multiple copies of the same form open at once!!

16. Two Ways to Address a Form in Code
Refer to the form by it’s name
May refer to any public property or method of the form using FormName.PublicPropertyOrMethod
FormName.lblCustomerID.Text = …
FormName.Show
FormName.Text = …
Any changes made to a property or value this way
Persist as long as the application is running
(unless explicitly changed elsewhere)

17. Two Ways to Address a Form in Code (cont.)
Create an object variable instance of the form
The copy of the form created in the variable (theFormName in the example above) only lasts as long as the variable is in existence
Follows normal variable scoping rules
Any settings made to the copy expire when the object variable expires
New copies will revert to the form’s definition from design view
Dim theFormName as New FormName
theFormName.lblCustomerID.Text = …
theFormName.Show

18. Passing Values Between Forms
Forms expose certain elements to code on other forms or in other classes or modules
All controls
Because controls are declared in the form designer scoped with “Friend”
Any variable or custom-written property declared with
Public
Available to any code
Friend
Available to any code in the same project

19. Passing Values Between Forms (cont.)
Public Class FormB
Friend intCustomerID as Integer
If the declaration above exists on Form B code on Form A can address intCustomerID directly
Any code on Form B can then read this value
Common to read the value in the Form Load event but it can be read anywhere
Code on other forms can also read the value
“Friend” cannot be used in a procedure
‘* Code on Form A
FormB.intCustomerID = Convert.ToInt32(txtCustID.Text)

20. Passing Values Between Forms (cont.)
Any form or control property on any form can be set or read by code on another form
FormName.PropertyName
FormName.ControlName.PropertyName
We can also write Friend scoped custom properties for forms
Covered in the Object Oriented classes later in the semester

21. Returning to The Correct Form
In a straight hierarchical navigation structure managing return to the correct form is straightforward
Form A can use FormB.ShowDialog to show Form B
Focus will be returned to Form A when Form B is released
Or Form B can explicitly show Form A because it is the only form that will ever open Form B

22. Returning to the Correct Form (cont.)
If both Form A and Form B (or any other form) both open Form C
On Form C put this code
Public Class FormC
Friend theCallingForm As Form
Private Sub btnClose_Click...
theCallingForm.Show()
Me.Close()
End Sub
End Class
Note object declared as
type Form

23. Returning to the Correct Form (cont.)
Flexible form navigation (cont.)
On the calling form use this code
Form C now has a reference to the form that called it
Note that you cannot CLOSE the calling form or the called form will have no form reference
Private Sub btnFormC_Click...
Dim theFormC As New FormC
theFormC.theCallingForm = Me
theFormC.Show()
Me.Visible = False
End Sub
Do not close the calling form

24. Dialogs
VB comes with a rich collection of dialogs with which to create
Interactive mini-forms
Input box
Message box
Special purpose input forms
Splash screens
About box
Explorer form

25. Dialogs—Message Boxes
Message Boxes return a value indicating which button was pushed
Button combinations
AbortRetryIgnore OK
OKCancel
RetryCancel
YesNo
YesNoCancel
Return Values
1 = OK
2 = Cancel
3 = Abort
4 = Retry
5 = Ignore
6 = Yes
7 = No

26. Dialogs—Message Boxes (cont.)
Message boxes can be called as a statement or used in a function format to return a value
Experiment with the wide variety of icons
Avoid using message boxes excessively
lblMessageBoxResult.Text = MessageBox.Show("Show the message", _
"Click the Buttons", _
MessageBoxButtons.RetryCancel, MessageBoxIcon.Question, _
MessageBoxDefaultButton.Button1)

27. Dialogs—Input Boxes
An input box displays a fixed size mini form with OK and Cancel buttons and a single text input area
Returns the contents of the text area if the OK button is pressed
Returns an empty string
If the Cancel button is pressed
If the text input area is empty

28. Dialogs—Custom Dialog Forms
Any form can work like a dialog box with any combination of controls
Set the form’s .DialogResult property to one of the available DialogResult values
Consider setting the MinimizeButton, MaximizeButton, and ControlBox properties to False and set the FormBorderStyle to Fixed Single
Private Sub btnOK_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnOK.Click
Me.DialogResult = Windows.Forms.DialogResult.OK
Me.Close()
End Sub

29. Dialogs—Custom Dialog Forms (cont.)
Read the custom dialog form’s .DialogResult property in the calling form and take appropriate action
Other public or friend values on the custom dialog form are also available after it has closed
Dim theCustomDialog As New CustomDialog
theCustomDialog.ShowDialog()
If theCustomDialog.DialogResult = Windows.Forms.DialogResult.OK Then
lblCustomDialogResult.Text = theCustomDialog.cboColor.Text
Else
lblCustomDialogResult.Text = "Cancelled“
End If

30. Dialogs—Built in Dialogs
There are several built in dialogs available in VB
Each returns a specialized value
ColorDialog returns a Color
FontDialog returns a Font
FileDialog, OpenFileDialog, & SaveFileDialog return a file path
See sample code for two examples
We will use the file dialogs in the Sequential Data File classes

31. Splash Screens
Many programs have splash screens
VB provides a built-in splash screen but I prefer to make my own
Requires use of the Timer control
Make the splash screen the Start Up form
Have the timer tick event open the next form (usually menu) and close the splash screen
Hint: Set the timer interval to be very short during development

32. Timer Controls
Timer controls appear in the resource area at the bottom of the form design area
Tick property indicates how many clock ticks measured in milliseconds will count down before the timer’s Tick event executes
Value of 1000 = one second
The timer’s Start method must be called before the timer will start counting
The Tick event contains code to run when the specified interval has passed

33. Miscelaneous
Remember to always Open the next form before closing the current form
If the project is set to end after the last form closes you could inadvertently end the program
Avoid situations where you are leaving open forms behind you
Use “Close” or “Menu” to indicate this form will close but you will return to a higher form
Use “Exit” to indicate that the program will end
It is good practice to have only one place to end the program