In some cases, two or more containers can be used to implement the same functionality. In some other cases, your choice will be narrowed based on your goal.

The most common and the most widely used container is the form. In an application, a form can be configured to display like a regular dialog box, to become a Single Document Interface (SDI) or to participate in a Multiple Document Interface (MDI) application.

As mentioned already, there are two categories of controls: parents and children:

• Parent: The child controls are positioned on a parent. To keep track of its children, a parent control has the Controls property. To create a control inside of a parent, a child control is added to the Controls property of the parent using the Controls.Add() method. When a parent control is created, it "gives life" to other windows that can depend on it. When a parent is destroyed, it also destroys its children. A parent control "carries", "holds", or hosts the controls positioned on it. When a parent is created, made active, or made visible, it gives existence and visibility to its controls. When a parent gets hidden, it also hides its controls. If a parent moves, it moves with its children. The controls keep their positions and dimensions inside the parent. The .NET Framework provides various parent controls.
• Child: A window is referred to as child when its existence, its visibility, and its availability depend on another window referred to as its parent. Except for the forms, all of the Windows controls you will use in your applications are child controls and they must be parented by another control.

A child window can be a parent of another control. For example, the Standard toolbar of Visual Studio 2005 is the parent of the buttons on it. If you close or hide the toolbar, its children disappear. At the same time, the toolbar is a child of the application's form. If you close the application, the toolbar disappears, along with its own children. In this example, the toolbar is a child of the form but is a parent to its buttons.

The type of container you want to use dictates how you acquire that container and add it to your application. Parent controls are somewhat divided in two broad categories: primary parents and intermediate parents. Once you have spent time with them, you will decide which one and when to use a particular control.

The primary type of control parenting you will use is a form. This is used as the platform for other controls, including other containers. Therefore, when you start your application, you first decide on the type of application. If you create a Windows Forms application, it gets automatically equipped with a form on which you can add child controls. When the application executes, it can present its contents to the user:

The second category of parents you will encounter qualify as intermediate. Theses containers cannot be the base of an application as does the form. These parents must be positioned on another parent first, then they can host their own children. An example of such a parent is the property page also called tab control. This control must be hosted by a form or dialog box. Here is an example of a property sheet (dialog box) that hosts three property pages (tab controls) and each property page hosts its own child controls:

Another type of intermediary container is the toolbar that is usually used to host various buttons.

A dialog box is a form defined with particular properties. Like a form, a dialog box is referred to as a container. Like a form, a dialog box is mostly used to host child controls, insuring the role of dialog between the user and the machine. Here is an example of a dialog box:

A dialog box has the following characteristics:

• The only system button it is equipped with is Close . As the only system button, this button allows the user to dismiss the dialog and ignore whatever the user would have done on the dialog box
• It cannot be minimized, maximized, or restored. A dialog box does not have any other system button but Close
• It is usually modal, in which case the user is not allowed to continue any other operation on the same application until the dialog box is dismissed
• It provides a way for the user to close or dismiss it

1. Start Microsoft Visual Basic and create a new Windows Application named SolasPropertyRental1
2. From the Common Controls section of the Toolbox, click ListView and click the form
3. While the list view is still selected, in the Properties window, change the following characteristics
   (Name): LvwProperties
   View: Details
4. Still in the Properties window, click Columns and click its ellipsis button
5. In the ColumnHeader Collection Editor, click Add
6. In the right list, click Text and type Property #
7. Click Add.
   In the right list, click Text and type Property Type
8. Click Add.
   In the right list, click Text and type Bedrooms
9. Click Add.
   In the right list, click Text and type Bathrooms
10. Click Add.
    In the right list, click Text and type Monthly Rent
11. Click OK
12. Complete the design of the form as follows:
     

    Control Text Name ListView     Button New Property... BtnNewProperty Button Close BtnClose

13. To add another form to the project, on the main menu, click Project -> Add Windows Form...
14. In the middle list, make sure Windows Form is selected.
    Set the Name to PropertyEditor and click Add

To create a dialog box, you start with a form, which you can get by creating a Windows Application or deriving a class from Form. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()
            Text = "Domain Configuration"
            Width = 320
            Height = 150
            Location = New Point(140, 100)
            StartPosition = FormStartPosition.CenterScreen
        End Sub

    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

This would produce:

There are a few actions you should perform on a form to transform it into a dialog box; but normally, these are only suggestions, not rules. Based on the Microsoft Windows design and standards, to create a dialog box, you should set a form's FormBorderStyle property to FixedDialog. Setting this property changes the borders of the form to the standard borders of a dialog box (the border of a dialog box is thinner than that of a regular form). You can set this characteristic in the Properties window or programmatically. Here is an example:

Public Sub InitializeComponent()
            Text = "Domain Configuration"
            Width = 320
            Height = 150
            Location = New Point(140, 100)
            StartPosition = FormStartPosition.CenterScreen

            FormBorderStyle = Windows.Forms.FormBorderStyle.FixedDialog
End Sub

Besides taking care of the border, you should also set both the MinimizeBox and the MaximizeBox properties to False. This causes the window to display only the system Close button. You can set these characteristics in the Properties window or programmatically. Here is an example:

Public Sub InitializeComponent()
            Text = "Domain Configuration"
            Width = 320
            Height = 150
            Location = New Point(140, 100)
            StartPosition = FormStartPosition.CenterScreen

            FormBorderStyle = Windows.Forms.FormBorderStyle.FixedDialog
            MinimizeBox = False
            MaximizeBox = False
End Sub

This would produce:

1. To transform the PropertyEditor form into a dialog box, in the Properties window, change its characteristics as follows:
   FormBorderStyle: FixedDialog
   StartPosition:        CenterParent
   MinimizeBox:         False
   MaximizeBox:        False
   ShowInTaskbar:    False
2. Design the dialog box as follows:
    

   Control Text Name Label Property Type:   TextBox   TxtPropertyType Button Cancel BtnCancel Label Bedrooms:   TextBox   TxtBedrooms Button OK BtnOK Label Bathrooms:   TextBox   TxtBatrooms Label Monthly Rent:   TextBox   TxtMonthlyRent

You should provide a way for the user to close the dialog box. A dialog box should have at least one button labeled OK. This button allows the user to acknowledge the message of the dialog box and close it by clicking the button. If the user press Enter, the dialog box should also be closed as if the OK button was clicked.

Often the user will be presented with various options on a dialog box and may be asked to make a decision on the available controls. Most of the time, if you are creating such a dialog box, besides the OK button, it should also have a Cancel button. The OK button should be the default so that if the user presses Enter, the dialog box would be closed as if the user had clicked OK. Clicking OK or pressing Enter would indicate that, if the user had made changes on the controls of the dialog box, those changes would be acknowledged and kept when the dialog box is closed and usually the changed values of the control would be transferred to another dialog box or form. Keep in mind that you are responsible for implementing this functionality.

To fulfill this functionality of the OK button, after adding it to a dialog box (or form), open the AcceptButton combo box in the Properties window for the form and select the name of the button.

1. Click an unoccupied area of the form
2. In the Properties window, click the arrow of the AcceptButton field and select BtnOK

The Cancel button is used to allow the user to dismiss whatever changes would have been made on the controls of the dialog box. The dialog box should also be configured so that if the user presses Esc, the dialog box would be closed as if the user had clicked Cancel.

To fulfill this functionality of the Cancel button, after adding it to a dialog box (or form), open the CancelButton combo box in the Properties window for the form and select the name of the button.

Besides the OK and the Cancel buttons, a dialog box can be created with additional buttons such as Finish or Help, etc. It depends on its role and the decision is made by the application developer.