1. Multi-form applications and dialogs
Secondary Forms
Multiform Applications
November 17, 2018

2. Multiform applications
Nearly all desktop GUI applications use more than a single form to do their jobs
Visual Studio has the editor with many fly-out panels, dialogs to open or create projects, classes, resources, and so forth, save them, close them, debug them, and so forth
Word processors have open/save/save as dialogs, select font or color dialogs, about boxes, and so forth
Even browsers may have multiple sites open in different tabs, pop-up security messages or ads, and so forth
Many applications have splash screens and about boxes at a minimum
Multiform Applications
November 17, 2018

3. Common Dialogs
Some dialogs are so commonly needed among applications, that .NET supplies prewritten classes for you to use in such cases
Tasks such as Opening or Saving a File, Selecting a Font, Choosing a Color, Displaying a Message in a MessageBox, and so forth are good candidates for such dialogs
Among the common dialogs provided by the .NET class library are OpenFileDialog, SaveFileDialog, ColorDialog, FontDialog, PrintDialog, MessageBox, and PageSetupDialog
These may be used as they are or tailored to suit the needs of the developer
Multiform Applications
November 17, 2018

4. Example Create new instance of ColorDialog
If user did not dismiss by canceling the operation
Display dialog
Get selected color
Multiform Applications
November 17, 2018

5. Select color and click OK
Example
Color Dialog
Result
Select color and click OK
Multiform Applications
November 17, 2018

6. OpenFileDialog
Multiform Applications
November 17, 2018

7. OpenFileDialog Example
Create dialog instance
Caption for the dialog
Filter: limits which files show in the dialog
If the user Canceled the dialog, simply return; otherwise process the selected file
When dialog first opens, initial directory is folder where app’s .exe is found
Filter contains sequences of “description|*.ext” where “description” is a phrase that will be shown describing what is being shown and “*.ext” specifies which file extensions are shown
Multiform Applications
November 17, 2018

8. OpenFileDialog Example
Caption
Initial Directory
Dropdown filter ComboBox Expanded
Only .txt files shown
Filter
Multiform Applications
November 17, 2018

9. SaveFileDialog
Multiform Applications
November 17, 2018

10. SaveFileDialog Example
Create instance
Set initial directory, caption, and filters
Display dialog, and, if not cancelled by user, process the selected file
Multiform Applications
November 17, 2018

11. SaveFileDialog Example
Caption
Initial Directory
Only *.txt files shown
Filter
Multiform Applications
November 17, 2018

12. FontDialog
Multiform Applications
November 17, 2018

13. FontDialog Demo Create instance
Set minimum and maximum allowable font sizes
Initial font set to current font
If user selected a font and did not cancel, make the label use that font
Multiform Applications
November 17, 2018

14. FontDialog Example Click Button Multiform Applications
November 17, 2018

15. Right click on project, choose Add, Windows Form…
Secondary Forms
Right click on project, choose Add, Windows Form…
The developer may also create new secondary forms
From the Solution Explorer, add a new Form to the project
Add new form
Multiform Applications
November 17, 2018

16. Pre-built, modifiable About Box
Secondary Form
Ordinary Form
Pre-built, modifiable About Box
Give it a suitable name
Multiform Applications
November 17, 2018

17. Secondary Form
The secondary form looks just like the main form initially
Developer may add controls, write event handlers, and so forth in the same ways as with the primary form
Multiform Applications
November 17, 2018

18. Communicating Between Forms
Primary creates an object of Secondary and displays it
The primary and secondary forms are just objects of classes and they interact just like ordinary objects. Do not let the fact that they are form objects make them mysterious
Passes Parameters to methods of Form2
Primary Form
Secondary Form
Return values and exposes public properties
Primary knows about, creates, and uses secondary. Secondary knows NOTHING about primary.
Multiform Applications
November 17, 2018

19. Example: Communicating Between Forms
Primary form sets some properties of secondary form
Primary form instantiates an object of secondary form
Primary form displays the secondary form . . .
There is no difference in dealing with a developer-created form and a built-in dialog
Multiform Applications
November 17, 2018

20. Using Secondary Forms
Can use Show or ShowDialog from one form to display an instance of another
Modal dialog must be dismissed before continuing with the parent form
Show yields a modeless dialog, while ShowDialog yields a modal dialog
Modeless dialog does not “block” the parent and user may switch back and forth between them
Multiform Applications
November 17, 2018

21. Setting the Result of a Dialog Box
The way a dialog box is closed, or its "result," can be set at either design time or run time:
At design time, you can set the DialogResult property for the Button controls on a dialog box
Setting the DialogResult property at run time allows you to dynamically handle user responses
To set the DialogResult property for a control at design time:
Click on the Button control whose property you want to set
Select the DialogResult property in the Properties window and open the list of available property settings
Select the appropriate DialogResult value
Lecture 9 - CSCI 3800: Forms and Dialogs
11/17/2018

22. Setting Results of a Dialog Programmatically
You can set the dialog box result for user-performed actions other than clicking a Button control. If your dialog box does not contain buttons to close the dialog box, you can set the result of the dialog box at run time.
To set the DialogResult property for a control or form programmatically
Navigate to the event handler or method in which you want to set the DialogResult property.
Type code similar to the following:
this.DialogResult = DialogResult.Yes;
// OR – for a button
btnNo.DialogResult = DialogResult.No;
Although setting the DialogResult property will cause your dialog box to close automatically, you can still finish handling the control's Click event, and the dialog box will close once the event handler's code is completed.
Lecture 9 - CSCI 3800: Forms and Dialogs
11/17/2018

23. Using a Secondary Form
Typically, the logic of an application may dictate that one form may “own” another form in the sense that the first form decides when to create, show, and use the second form
The first form often uses second form as result of some user action such as
Selecting a choice (such as Open, Save, Print, Select Font, About, Help, and so forth) from a main Menu or a context Menu
Clicking a button
Selecting something from a ListBox or ComboBox
The second form may also use secondary forms of its own
In the event handler for the event that results in the display of the second form, an instance of the second form is created, and it is displayed through a call to a method such as Show or ShowDialog …
Multiform Applications
November 17, 2018

24. Creating and Using a Secondary Form
From within an Event Handler in one Form, the code below may be used to create and display a second Form
Create instance of the second form
Display the second form
Use results of work done by second form here in the first form
Multiform Applications
November 17, 2018

25. Using a Secondary Form
In some cases, however, there may be a second form that is independent of all other forms
No other form decides when to display it
No other form creates an instance of it or uses its methods and properties
A splash screen may be such a form
In such a case, the secondary form may be “owned” by the application rather than by another form
In this case, it may be opened by some method such as Main in the driver program
Multiform Applications
November 17, 2018

26. Independent Secondary Form
Create and show splash screen form . . .
… then, create and show the primary form for the application
Note that these are sequential operations. The primary form will not be created and shown until the SplashForm has been closed
Multiform Applications
November 17, 2018

27. Replaceable picture in PictureBox
Using the AboutBox
VS provides a skeleton of an AboutBox form that is usable as it is, but it may also be tailored to suit the application
These items are filled-in at run-time from AssemblyInfo.cs by the code that is provided
Replaceable picture in PictureBox
Multiform Applications
November 17, 2018

28. Generated/Modified Code
Description modified
Default picture is replaced
Multiform Applications
November 17, 2018

29. AboutBox Example Results
Multiform Applications
November 17, 2018

30. Splash Screen
One may remove the border and caption via the FormBorderStyle property if desired
Ordinary form with a Split Container control docked to fill the form
One Panel of the Split Container has a Picture Box
Transparency may be achieved by setting the TransparencyKey property
The other panel has a Label for the Program Name …
… and another for the version number
Uses a timer to dismiss itself
Multiform Applications
November 17, 2018

31. Transparent Borderless Form
Remove the border from around the form
Everything that is white in the design will be transparent when the form is displayed at run time
Multiform Applications
November 17, 2018

32. Borderless, Transparent Form
Multiform Applications
November 17, 2018

33. The Code in the Splash Screen Class
Timer interval is set to 3.5 seconds in this case
Multiform Applications
November 17, 2018

34. Code in the Driver
Primary form is not displayed until after the Splash Screen form closes itself
Multiform Applications
November 17, 2018