How to (best) detect siting of a control?

[jmsrickland]

Since OP wants to detect the presence/absence of controls at design time then there is no code involved so things like WM_CONTROL_ADDED, WM_CONTROL_REMOVED or WM_CONTROL_CHANGED, "....what I need is to detect a change in the forms controls collection.", etc are meaningless since your program is not running if I understand OP

[7edm]

Since OP wants to detect the presence/absence of controls at design time then there is no code involved so things like WM_CONTROL_ADDED, WM_CONTROL_REMOVED or WM_CONTROL_CHANGED, "....what I need is to detect a change in the forms controls collection.", etc are meaningless since your program is not running if I understand OP

Not entirely correct, UserControl code executes both at run-time and design-time, but I wasn't clear of that either before I started to dive in to this.