For a UserControl there is the 'Load event you can exploit to make sure the
internal structure of your control that inherits from a built-in WinForms
control is setup properly, most likely based on the user's changing the public
properties you have exposed to the IDE designer.

But for a control class that inherits from a built-in WinForms control, there is
no Load event exposed.

If you make a "compound" control : something where the Class inherits from a
built-in Windows Form UI control like :

       public class  ExtendedListView : System.Windows.Forms.ListView
      {
           // yada ... yada ...
       }

And instantiate it, and set its properties, size it, etc. only from code : no
problems.

But when you go to the trouble of putting a ToolBox icon into it, and then
mounting it in the ToolBox where you want to select, drag, and drop it on
various container objects :

   1. The constructor will be called twice :  once at the moment of dropping it
on the container : again at the moment you 'run' the form
       or project that instantiates and activates the container.

I've experimented with a variety of techniques (found here, on CodeProject,
etc.) that are designed to detect the difference between run-time and
design-time :  these don't appear to work in this scenario.

I've tried the following types of coding techniques to no avail :

// doesn't work
protected override void OnHandleCreated(EventArgs e)
{
   base.OnHandleCreated(e);
   Form parentForm = this.FindForm();
   if(parentForm != null)
   {
       if(parentForm.IsHandleCreated)
       {
           CreateUI();
       }
   }
}

// doesn't work
if(Parent != null && ! Parent.IsDisposed)
{
   if(Parent.IsHandleCreated)
   {
       CreateUI();
   }
}

// doesn't work
if(this.IsHandleCreated)
{
       CreateUI();
}

// doesn't work
if(this.Site != null)
{
   if(this.Site.DesignMode == false)
   {
       CreateUI();
   }
}

Appreciate your advice !

Bill Woodruff
dotScience
Chiang Mai, Thailand