1. Multiple Document Interface (MDI) application
Part 1

2. Objectives Understand the characteristics of MDI applications
Organize the procedures between forms in MDI applications
Understand the role of standard forms in an MDI application
Integrate menus in an MDI application and create context menus
Understand the relationships between events in an MDI application
Manage and organize the forms that make up an MDI application

3. Solution Organization

4. Characteristics of MDI Programs
Single-document interface applications
Create one instance of a particular form
Multiple-document interface (MDI) applications
Create multiple instances of the same form
Display those multiple form instances such that they appear inside the region of another form
Excel is an MDI application, for example

5. MDI Applications
You can use three different types of forms in an MDI application
An MDI parent form acts as the container for the MDI child forms in the solution
An MDI child form always appears inside the visible region of its MDI parent form
A project may have one or more MDI child forms
Standard forms can be displayed anywhere on the screen and are not contained by the MDI parent form
Standard forms are typically displayed as dialog boxes

6. Characteristics of MDI Applications
MDI child forms can not be extended beyond the visible region of the containing MDI parent form
Iconified MDI child forms do not appear on the task bar
The user positions the icon inside the visible region of the MDI parent form
Menus of MDI parent and MDI child forms are integrated

7. Displaying an MDI Child Form
Code to create MDI child form appears in MDI parent form
Create the child form instance
Dim frmCurrentChild As New frmMdiChild()
Designate the form as a child form
frmCurrentChild.MdiParent = Me
Display the child form
frmCurrentChild.Show()

8. Organizing Procedures in MDI Applications (1)
The following list describes the problems shared by nearly all MDI applications
Procedures and data must often be shared by both MDI parent forms and MDI child forms
An MDI parent form often needs to know which MDI child form instance is active
From the MDI child form, you must often reference members of the MDI parent form or the MDI parent form itself

9. Organizing Procedures in MDI Applications (2)
When organizing the procedures and variables in an MDI application, consider the following rules
Locate the procedures that create instances of the MDI child forms in the MDI parent form
In the MDI child form(s), create the procedures responsible for managing each instance of the MDI child form
To share a global reference to the MDI parent form, declare a Friend or global variable in a module file
When the MDI parent form loads, store a reference to the MDI parent form in the Friend or global variable

10. Standard Forms in MDI Applications
MDI applications can have standard forms
Characteristics
Standard forms typically do not have menus
Standard forms are typically displayed as modal dialog boxes

11. Menus and MDI Applications
Each MDI parent form and any MDI child form in a solution can have its own menu system
MDI application menus have unique characteristics
One menu bar appears below the title bar of the MDI parent form
An MDI parent form’s menu appears when no MDI child forms are loaded
When an instance of an MDI child form is loaded or has focus, the menu of the MDI parent form is merged with the menu of the MDI child form
Standard forms in an MDI application can have an associated menu but typically they do not

12. Merging Menus
Menus of MDI parent and MDI child forms are merged based on the following property values:
MergeOrder property
Applies to a MenuItem and contains an Integer value
Indicates the relative order in which two menus or menu items will be merged
MergeType property
Works in conjunction with the MergeOrder property
Defines whether one menu will replace another menu, whether one menu will be added to another menu, or whether menu items will be merged together

13. The MergeType Property
The MergeType property has a data type of MenuMerge
Possible enumeration values
Add - menu on the MDI child form will be added to the menu of the MDI parent form
MergeItems - menu items on the MDI child form menu will be merged with the menu items on the MDI parent form menu
Remove - MDI parent form menu or menu item will not appear in the merged menu
Replace - causes the menu of the MDI child form to replace the menu appearing on the MDI parent form

14. Merging Menus (1)

15. Merging Menus (2)

16. Merging Menus (3)

17. Using Menus to Select MDI Child Forms
To select and display an MDI child form from a menu
Set the MdiList property of a menu item to True
This setting causes the menu item to display a list of MDI child form instances
The caption appearing in the menu is the same as the caption appearing in the title bar of the MDI child form
The process is automatic - you need not write any statements to display the MDI child forms

18. Arranging MDI Child Forms
The LayoutMdi method applies to the MDI parent form
Use to configure display of child forms
Four valid enumeration values
ArrangeIcons - iconified MDI child windows are arranged along the bottom of the MDI parent form
Cascade - visible MDI child windows are arranged such that each MDI child window appears below another MDI child window and is indented
TileHorizontal - divides the MDI child forms horizontally to fill the visible region of the MDI parent form
TileVertical - divides the MDI child forms vertically to fill the visible region of the MDI parent form

19. Context Menus
Context menus typically appear when the user right-clicks on a control instance or the form itself
To create a context menu:
Create an instance of the ContextMenu control
Create the menu items in-place
Associate the context menu with a form or control instance by setting the ContextMenu property of the desired form or control instance to the context menu

20. Context Menus (Illustration)
Context menu title cannot be changed
Menu items

21. MDI Event Relationships
Windows fires various events as the user navigates from form to form in an MDI application
Events
The Closing event fires for both the MDI parent and MDI child forms
Fires first for all children and then the parent
Event can be cancelled
The Enter event fires for the MDI child form getting focus
Use to update status information
The Leave event fires just before an instance of the MDI child form loses focus

22. Order of Closing Events

23. Managing MDI Child Forms
There is no Forms collection to manage the loaded MDI forms of an application
Create a class to enable the developer to add and remove forms from the collection, and enumerate the collection with a For Each loop

24. Summary MDI application consists of Child forms
MDI form and multiple MDI child forms
Child forms
Can be multiple instances of the same class, or each child can be an instance of different classes
Basics of building an MDI application
Designate one form as an MDI form by setting its IsMdiContainer property to True
Add another form (Form2) to the project, which becomes a child form
Because the form is defined as a class, the (parent) MDI form must instantiate a new (child) form2 (Form2Temp)
Declare Form2Temp’s MdiParent property to be the MDI form itself
Finally, show Form2Temp