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Software

ActiveX Objects and Controls - Visual Basic 6.0

Table of Contents [Hide/Show]    Basics       Project Properties       Procedure Attributes    ActiveX Controls       Life Cycle       Control Properties       Extender Object       Ambient Object       Property Persistence          Method          Code Sample       Standard Events       Custom Events       Property Pages

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Basics¶

Project Properties¶

Item	Description
Project Name	the project as seen in both the Object Browser and code
Help File Name
Project Help Context ID
Project Description	the description as it appears in the Project References dialog, so it should be a user-friendly description.
Application Title (Make tab)	the title as it appears in the Task Manager

Procedure Attributes¶

Item	Description
Description	as it appears in the Object Browser
Help Context ID	the help context ID for this procedure. (See project properties, above, to specify the help file)
Procedure ID	(Default) = the default property if none is specified Caption = property will update dynamically on the form as the user types –4 = enumeration property

ActiveX Controls¶

Life Cycle¶

State	Notes
Control Design-time	no control events are triggered
Host Design-time; Control Run-time	closing the object design window for the ActiveX control enables its button on the VB Toolbox, and initializes the ActiveX control object. Opening the object design window again disables the VB Toolbox button, and terminates the ActiveX control object.
Host Run-time; Control Run-Time

Control Properties¶

Property	Description
Project Name	the name of the type library for the compiled OCX file
Project Description	the text the users will see when displaying a list of all installed ActiveX components
Name	becomes the class name for the control

Extender Object¶

Apparent built-in properties such as Name, Top, Left, and Visible are provided by the Extender object. Not all host apps extend the same properties with their Extender objects, and some apps don’t support the Extender object at all (e.g., Access 97 and Internet Explorer 3.0). Use the Extender object only with error-handling!

Ambient Object¶

The Ambient object corresponds to the form hosting your UserControl. It is used to determine properties of the host form so that those properties can be assimilated by the control.

Property Persistence¶

Method¶

Use the PropertyChanged "property-name" statement to tell the Properties window to update its display, and to tell VB that the form’s property storage has changed. Note: In an ActiveX Document, use the PropertyChanged routine without an argument

• Persist changed properties in the WriteProperties event using the PropertyBag.WriteProperty method
• Load persisted properties in the ReadProperties event using the PropertyBag.ReadProperty method
  

Code Sample¶

Property Let Active(x as Boolean)
   timMain.Enabled = x
   PropertyChanged "Active"
End Property

Private UserControl_WriteProperties(PropBag as PropertyBag)
  ' Repeat the following line for each property
  PropBag.WriteProperty "Active", timMain.Enabled, True
End Sub

Private UserControl_ReadProperties(PropBag as PropertyBag)
  ' Repeat the following line for each property
  Active = PropBag.ReadProperty("Active", True)
End Sub

Standard Events¶

Event	Occurs	Purpose
Resize	As the control is resized, including when it is first placed on a form at Host Design Time	Allow code to resize constituent controls
InitProperties	Only once: when the control is instantiated at Host Design-Time	Initializes properties when you insert an instance of the control onto a form at Host Design-Time only
AmbientChanged	When certain properties of the host form change	To allow the UserControl to assimilate properties of the host form
WriteProperties	Just before VB destroys the instance of the running control at Host Design-Time	To retrieve changes to the ActiveX control and persist them into the form’s storage
ReadProperties	Just before VB instantiates the control at Host Design Time	To retrieve property settings for the ActiveX control from the form’s storage and apply them to the control

Custom Events¶

• Events are declared in the General Declarations section
  

• Events are raised in the control’s code module
  

Property Pages¶

• You must define custom properties before a Property Page can be defined.
• Double click on your UserControl in the Project window to select it.
• On the Add-Ins menu, click Property Page Wizard. If it is not available, click Add-In Manager at the bottom of the menu to add it.
  

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Portions of this article were taken from AppDev Advanced Visual Basic 5.0, Chapter 33