Q177627: HOWTO: Use the OLE_OPTEXCLUSIVE Property Data Type
Article: Q177627
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbnokeyword kbVBp500 kbVBp600 kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Control Creation Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
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SUMMARY
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An ActiveX control property can be any valid data type, such as long or string.
Visual Basic provides some special data types for ActiveX control properties,
such as OLE_OPTEXCLUSIVE. This article demonstrates how to use the
OLE_OPTEXCLUSIVE data type.
MORE INFORMATION
================
The OLE_OPTEXCLUSIVE data type is internally represented as a Boolean, with
valid values True and False. However, what makes OLE_OPTEXCLUSIVE unique is that
if several controls of this data type are placed within a container (such as a
Frame or Form), only one member of the group will be capable of being set to
True, all others will be set to False.
For example, you could use an OLE_OPTEXCLUSIVE control if you created a option
group with three options (Paper, Scissors, and Rock), where users can only
select one of the three choices. Basically, when controls of this type are
placed into a container, they are expected to behave as an option button; no
more than one control can have its value set to True at any given time.
The steps below describe how to create a simple ActiveX control of type
OLE_OPTEXCLUSIVE.
Create ActiveX Control
----------------------
The following steps describe how to create an ActiveX control whose default value
will be of type OLE_OPTEXCLUSIVE. If its default value is set to True, its color
turns green. If its default value is set to False, its color turns red.
1. In Visual Basic, create a new ActiveX Control project.
2. From the Project menu, choose Project1 Properties. In the Project Name field,
type "OptExclusiveControl" without the quotes. Click OK.
3. Set the UserControl BackColor property to red (&H000000FF&). This
will be the default color for the UserControl.
4. View the code window for the UserControl and copy the following code:
Option Explicit
Private CurrentValue As OLE_OPTEXCLUSIVE
Private Sub UserControl_InitProperties()
'Set the initial value for the Value property to False...much
'like an option button would set its initial value to False
'(unselected).
Me.Value = False
End Sub
Private Sub UserControl_Click()
'When the User Clicks on the control, the Value property of the
'control will be set to True, just as an option button
'sets its value to True when it is clicked.
Me.Value = True
End Sub
Public Property Get Value() As OLE_OPTEXCLUSIVE
'Retrieve the current value of the Value property
Value = CurrentValue
End Property
Public Property Let Value(ByVal NewValue As OLE_OPTEXCLUSIVE)
'If the NewValue is True, the UserControls color is set
'to green and all other instances of the control within
'a container are set to False automatically.
'
'If NewValue is False, the UserControls color is set to red.
If NewValue = True Then
UserControl.BackColor = &HFF00& 'Green
CurrentValue = NewValue
PropertyChanged "Value" 'Notifies the container that the
'property has changed. If you exclude
'this line of code, the ActiveX
'control will not behave as an
'option group because there is no
'mechanism to inform the container
'that the property has changed.
Else
UserControl.BackColor = &HFF& 'Red
CurrentValue = NewValue
PropertyChanged "Value"
End If
End Property
5. From the Tools menu, choose Procedure Attributes.
6. In the Procedure Attributes window, be sure the Value property is selected in
the Name combo box, and then click Advanced.
7. For Procedure ID, choose (Default) from the drop-down list. Only one property
procedure can be set to the default. This becomes the default property for
your ActiveX Control. If you do not set the OLE_OPTEXCLUSIVE property to the
default value, it will not function as expected. In this example, the
property was named "Value" for simplicity. However, you can set any named
property procedure as your default.
8. Save the Project and compile the OptExclusiveControl.Ocx.
You now have an ActiveX Control whose data type is OLE_OPTEXCLUSIVE. The next
set of steps describe how to build a container to test the control.
Creating the Test Container
---------------------------
The test container is designed to test the OptExclusiveControl created in the
steps above.
1. Create a new Standard EXE project in Visual Basic. Form1 is created by
default.
2. From the Project menu, choose Components. Select the OptExclusiveControl
created in the above steps.
3. Add a Frame control to Form1.
4. Add three OptExclusiveControls to the Frame.
5. Run the Project.
When the project is running, Form1 will display the frame with three of the
OptExlcusiveControls on it. Clicking on a OptExclusiveControl turns its color
green. As you click on the other OptExlcusiveControls, notice that only one
OptExclusiveControl can be green at any given time.
NOTE: OLE_OPTEXCLUSIVE controls behave as such within a container. The example
above uses a frame to demonstrate the OLE_OPTEXCLUSIVE behavior. However, the
form itself could server as the container.
Additional query words:
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Keywords : kbnokeyword kbVBp500 kbVBp600 kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbZNotKeyword3
Issue type : kbhowto
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