Understanding Container and Control Objects

You can add the following types of objects to a form:

• Controls

• Containers

• User-defined classes

• Sharing Information and Adding OLE

Objects in Visual FoxPro belong in one of two categories, depending on the nature of the class they are based on:

• Containers can hold other containers or controls. They can act as the parent object for other objects. For example, a form, as a container, is the parent object of a check box on that form.

• Controls can be placed in containers, but cannot be the parent for other objects. For example, a check box cannot contain any other object.

The Form Designer allows you to design both containers and controls.

Container	Can contain
Column	Headers, and any objects except form sets, forms, toolbars, timers, and other columns
Command button group	Command buttons
Form set	Forms, toolbars
Form	Page frames, grids, any controls
Grid	Columns
Option button group	Option buttons
Page frame	Pages
Page	Grids, any controls

Collection and Count Properties

All container objects in Visual FoxPro have a count property and a collection property associated with them. The collection property is an array referencing each contained object. The count property is a numeric property indicating the number of contained objects.

The collection and count properties for each container are named according to the type of object that can be contained in the container. The following table lists the containers and the corresponding collection and count properties.

Container	Collection Property	Count Property
Application	Objects Forms	Count FormCount
FormSet	Forms	FormCount
Form	Objects Controls	Count ControlCount
PageFrame	Pages	PageCount
Page	Controls	ControlCount
Grid	Columns	ColumnCount
CommandGroup	Buttons	ButtonCount
OptionGroup	Buttons	ButtonCount
Column	Controls	ControlCount
ToolBar	Controls	ControlCount
Container	Controls	ControlCount
Control	Controls	ControlCount

These properties allow you to use a loop to programmatically manipulate all or specific contained objects. For example, the following lines of code set the BackColor property of columns in a grid to alternating green and red:

o = THISFORM.grd1
FOR i = 1 to o.ColumnCount
   IF i % 2 = 0 && Even-numbered column
      o.Columns(i).BackColor = RGB(0,255,0) && Green
   ELSE
      o.Columns(i).BackColor = RGB(255,0,0) && Red
   ENDIF
ENDFOR

See Also

Tasks

How to: Add Visual FoxPro Containers

How to: Add Visual FoxPro Controls to a Form

Concepts

Adding Objects to Forms