How To Detect When a Control Is Placed into a UserControl

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Step-by-Step Example

The following example creates a custom ActiveX control that can perform some action when another control is placed on top of it:

1. Start a new ActiveX Control project. UserControl1 is added by default.
2. Set the ControlContainer property to True.
3. Add a Timer control to UserControl1. Add the following code to the Timer event of Timer1:

         Private Sub Timer1_Timer()
            Dim UserCtrl As Object
            Debug.Print UserControl.ContainedControls.Count
            For Each UserCtrl In UserControl.ContainedControls
               Debug.Print UserCtrl.Name
            Next
   
         End Sub
   						

4. Set the Timer1 Interval property to 1000 so Private Sub Timer1_Timer() gets called every 1 second.
5. Close the UserControl1 design window.
6. Click Add Project on the File menu. Select "Standard EXE" and click Open.
   
   NOTE: You now have a project group consisting of an ActiveX control project and a Standard EXE project.
7. Click Immediate Window on the View menu.
8. Draw the UserControl1 (the control you just created in your group) on Form1.
9. Select any other control from the toolbox and put it on top of UserControl1.

RESULTS: When you draw another control on top of UserControl1, the count of how many controls you have added plus the name of each control appears in the Immediate Window.