Knowledge Base

BUG: Dynamic Private UserControl Extender Events Do Not Show

Article ID: 196131

Article Last Modified on 5/13/2003

APPLIES TO

Microsoft Visual Basic 6.0 Learning Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q196131

SYMPTOMS

If you declare the variable using early-binding syntax when you dynamically add an instance of a private UserControl, you cannot see or use any of the control's extender properties or events. You are only able to see and use the raw properties and events of the control (that is, those declared by the control itself).

CAUSE

Visual Basic 6.0 allows developers to dynamically add ActiveX controls to a form at run time. Typically, a VBControlExtender variable is used for the dynamically-added control, which performs late binding on the control. However, if the type of the control is known at compile time, you can declare the variable using early binding syntax like the following:

   Dim WithEvents MyCtl As MyUserControl

However, if MyCtl is a private UserControl, Visual Basic binds directly to the interface for the control itself, bypassing the control extender it normally adds for ActiveX controls. As a result, your code will not see or be able to use any extender properties and events.

RESOLUTION

Declare the variable for your dynamically-added control as VBControlExtender, and Use the extender to access your control late-bound.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

Create a new standard .exe project. Form1 is created by default.
From the Project menu, add a new UserControl to the project.

Add the following code to the User Control:

      Event Click()

      Private Sub UserControl_Click()
         RaiseEvent Click
      End Sub

      Public Property Get Color() As OLE_COLOR
         Color = UserControl.BackColor
      End Property

      Public Property Let Color(Value As OLE_COLOR)
         UserControl.BackColor = Value
      End Property

Close the User Control design window and open the code window for Form1.

Add the following code to the General Declarations section of Form1:

      Dim WithEvents MyCtl as UserControl1

Click on the Event list, and select MyCtl. You will only see the Click event. None of the extender events (for example, GotFocus, LostFocus, DragOver, and so forth) are available. Further, if you try to use any extender properties in code you will get an error. For Example:
```
       MyCtl.Visible = True 'This will cause a compile error.

                        
```

To make the extender events available, add the following code to Form1:

      Dim WithEvents MyCtl As VBControlExtender

      Private Sub Form_Load()
         Set MyCtl = Controls.Add("Project1.UserControl1", "myctrl")
         MyCtl.Move 1, 1
         MyCtl.Visible = True
         MyCtl.Color = &HFF0000
      End Sub

      Private Sub MyCtl_ObjectEvent(Info As EventInfo)
         MsgBox "This control event was fired: " & Info.Name
      End Sub

Before you run the project, go to the Project menu and select Project1 Properties. Click the Make, and clear the "Remove information about unused ActiveX controls" check box.
Save and run the project.

RESULT: Click on the user control. You will see a message box indicating that the event fired properly.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

190670 : HOWTO: Dynamically Add Controls to a Form with Visual Basic 6.0

190153 : INFO: Remove Information About Unused ActiveX Controls

Visual Basic Books Online: Component Tools Guide; UserControls

Keywords: kbbug kbctrlcreate kbpending kbactivexevents KB196131

Microsoft KB Archive/196131

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